diff --git a/engine/src/flutter/include/minikin/Layout.h b/engine/src/flutter/include/minikin/Layout.h
index 83eb963b717..cb68db9c3dd 100644
--- a/engine/src/flutter/include/minikin/Layout.h
+++ b/engine/src/flutter/include/minikin/Layout.h
@@ -59,7 +59,7 @@ struct LayoutGlyph {
 };
 
 // Internal state used during layout operation
-class LayoutContext;
+struct LayoutContext;
 
 enum {
     kBidi_LTR = 0,
diff --git a/engine/src/flutter/libs/minikin/Android.mk b/engine/src/flutter/libs/minikin/Android.mk
index 4d34c114702..c728b09b84e 100644
--- a/engine/src/flutter/libs/minikin/Android.mk
+++ b/engine/src/flutter/libs/minikin/Android.mk
@@ -50,6 +50,7 @@ LOCAL_MODULE := libminikin
 LOCAL_EXPORT_C_INCLUDE_DIRS := frameworks/minikin/include
 LOCAL_SRC_FILES := $(minikin_src_files)
 LOCAL_C_INCLUDES := $(minikin_c_includes)
+LOCAL_CPPFLAGS += -Werror -Wall -Wextra
 LOCAL_SHARED_LIBRARIES := $(minikin_shared_libraries)
 
 include $(BUILD_SHARED_LIBRARY)
@@ -61,6 +62,7 @@ LOCAL_MODULE_TAGS := optional
 LOCAL_EXPORT_C_INCLUDE_DIRS := frameworks/minikin/include
 LOCAL_SRC_FILES := $(minikin_src_files)
 LOCAL_C_INCLUDES := $(minikin_c_includes)
+LOCAL_CPPFLAGS += -Werror -Wall -Wextra
 LOCAL_SHARED_LIBRARIES := $(minikin_shared_libraries)
 
 include $(BUILD_STATIC_LIBRARY)
@@ -73,6 +75,7 @@ LOCAL_MODULE := libminikin_host
 LOCAL_MODULE_TAGS := optional
 LOCAL_EXPORT_C_INCLUDE_DIRS := frameworks/minikin/include
 LOCAL_C_INCLUDES := $(minikin_c_includes)
+LOCAL_CPPFLAGS += -Werror -Wall -Wextra
 LOCAL_SHARED_LIBRARIES := liblog libicuuc-host
 
 LOCAL_SRC_FILES := Hyphenator.cpp
diff --git a/engine/src/flutter/libs/minikin/FontCollection.cpp b/engine/src/flutter/libs/minikin/FontCollection.cpp
index 4c0070c2b1e..2c228802597 100644
--- a/engine/src/flutter/libs/minikin/FontCollection.cpp
+++ b/engine/src/flutter/libs/minikin/FontCollection.cpp
@@ -43,7 +43,7 @@ FontCollection::FontCollection(const vector<FontFamily*>& typefaces) :
     vector<uint32_t> lastChar;
     size_t nTypefaces = typefaces.size();
 #ifdef VERBOSE_DEBUG
-    ALOGD("nTypefaces = %d\n", nTypefaces);
+    ALOGD("nTypefaces = %zd\n", nTypefaces);
 #endif
     const FontStyle defaultStyle;
     for (size_t i = 0; i < nTypefaces; i++) {
@@ -72,7 +72,7 @@ FontCollection::FontCollection(const vector<FontFamily*>& typefaces) :
         mRanges.push_back(dummy);
         Range* range = &mRanges.back();
 #ifdef VERBOSE_DEBUG
-        ALOGD("i=%d: range start = %d\n", i, offset);
+        ALOGD("i=%zd: range start = %zd\n", i, offset);
 #endif
         range->start = offset;
         for (size_t j = 0; j < nTypefaces; j++) {
@@ -82,7 +82,7 @@ FontCollection::FontCollection(const vector<FontFamily*>& typefaces) :
                 offset++;
                 uint32_t nextChar = family->getCoverage()->nextSetBit((i + 1) << kLogCharsPerPage);
 #ifdef VERBOSE_DEBUG
-                ALOGD("nextChar = %d (j = %d)\n", nextChar, j);
+                ALOGD("nextChar = %d (j = %zd)\n", nextChar, j);
 #endif
                 lastChar[j] = nextChar;
             }
@@ -110,7 +110,7 @@ FontFamily* FontCollection::getFamilyForChar(uint32_t ch, uint32_t vs,
     }
     const Range& range = mRanges[ch >> kLogCharsPerPage];
 #ifdef VERBOSE_DEBUG
-    ALOGD("querying range %d:%d\n", range.start, range.end);
+    ALOGD("querying range %zd:%zd\n", range.start, range.end);
 #endif
     FontFamily* bestFamily = nullptr;
     int bestScore = -1;
diff --git a/engine/src/flutter/libs/minikin/FontFamily.cpp b/engine/src/flutter/libs/minikin/FontFamily.cpp
index dfd37fe5930..1ff5a6bce4b 100644
--- a/engine/src/flutter/libs/minikin/FontFamily.cpp
+++ b/engine/src/flutter/libs/minikin/FontFamily.cpp
@@ -258,8 +258,8 @@ const SparseBitSet* FontFamily::getCoverage() {
         }
         CmapCoverage::getCoverage(mCoverage, cmapData.get(), cmapSize);  // TODO: Error check?
 #ifdef VERBOSE_DEBUG
-        ALOGD("font coverage length=%d, first ch=%x\n", mCoverage->length(),
-                mCoverage->nextSetBit(0));
+        ALOGD("font coverage length=%d, first ch=%x\n", mCoverage.length(),
+                mCoverage.nextSetBit(0));
 #endif
         mCoverageValid = true;
     }
diff --git a/engine/src/flutter/libs/minikin/HbFaceCache.cpp b/engine/src/flutter/libs/minikin/HbFaceCache.cpp
index fde2fa869f2..235f7f1b0c2 100644
--- a/engine/src/flutter/libs/minikin/HbFaceCache.cpp
+++ b/engine/src/flutter/libs/minikin/HbFaceCache.cpp
@@ -18,6 +18,7 @@
 
 #include "HbFaceCache.h"
 
+#include <cutils/log.h>
 #include <hb.h>
 #include <utils/LruCache.h>
 
@@ -26,7 +27,7 @@
 
 namespace android {
 
-static hb_blob_t* referenceTable(hb_face_t* face, hb_tag_t tag, void* userData) {
+static hb_blob_t* referenceTable(hb_face_t* /* face */, hb_tag_t tag, void* userData) {
     MinikinFont* font = reinterpret_cast<MinikinFont*>(userData);
     size_t length = 0;
     bool ok = font->GetTable(tag, NULL, &length);
@@ -39,7 +40,7 @@ static hb_blob_t* referenceTable(hb_face_t* face, hb_tag_t tag, void* userData)
     }
     ok = font->GetTable(tag, reinterpret_cast<uint8_t*>(buffer), &length);
 #ifdef VERBOSE_DEBUG
-    ALOGD("referenceTable %c%c%c%c length=%d %d",
+    ALOGD("referenceTable %c%c%c%c length=%zd %d",
         (tag >>24)&0xff, (tag>>16)&0xff, (tag>>8)&0xff, tag&0xff, length, ok);
 #endif
     if (!ok) {
@@ -50,11 +51,6 @@ static hb_blob_t* referenceTable(hb_face_t* face, hb_tag_t tag, void* userData)
             HB_MEMORY_MODE_WRITABLE, buffer, free);
 }
 
-static unsigned int disabledDecomposeCompatibility(
-        hb_unicode_funcs_t*, hb_codepoint_t, hb_codepoint_t*, void*) {
-    return 0;
-}
-
 class HbFaceCache : private OnEntryRemoved<int32_t, hb_face_t*> {
 public:
     HbFaceCache() : mCache(kMaxEntries) {
@@ -62,7 +58,7 @@ public:
     }
 
     // callback for OnEntryRemoved
-    void operator()(int32_t& key, hb_face_t*& value) {
+    void operator()(int32_t& /* key */, hb_face_t*& value) {
         hb_face_destroy(value);
     }
 
diff --git a/engine/src/flutter/libs/minikin/Layout.cpp b/engine/src/flutter/libs/minikin/Layout.cpp
index 6d62d5d7d8e..3b140faa2b8 100644
--- a/engine/src/flutter/libs/minikin/Layout.cpp
+++ b/engine/src/flutter/libs/minikin/Layout.cpp
@@ -276,16 +276,17 @@ void Layout::setFontCollection(const FontCollection* collection) {
     mCollection = collection;
 }
 
-static hb_position_t harfbuzzGetGlyphHorizontalAdvance(hb_font_t* hbFont, void* fontData, hb_codepoint_t glyph, void* userData)
-{
+static hb_position_t harfbuzzGetGlyphHorizontalAdvance(hb_font_t* /* hbFont */, void* fontData,
+        hb_codepoint_t glyph, void* /* userData */) {
     MinikinPaint* paint = reinterpret_cast<MinikinPaint*>(fontData);
     MinikinFont* font = paint->font;
     float advance = font->GetHorizontalAdvance(glyph, *paint);
     return 256 * advance + 0.5;
 }
 
-static hb_bool_t harfbuzzGetGlyphHorizontalOrigin(hb_font_t* hbFont, void* fontData, hb_codepoint_t glyph, hb_position_t* x, hb_position_t* y, void* userData)
-{
+static hb_bool_t harfbuzzGetGlyphHorizontalOrigin(hb_font_t* /* hbFont */, void* /* fontData */,
+        hb_codepoint_t /* glyph */, hb_position_t* /* x */, hb_position_t* /* y */,
+        void* /* userData */) {
     // Just return true, following the way that Harfbuzz-FreeType
     // implementation does.
     return true;
@@ -709,7 +710,7 @@ void Layout::doLayoutRun(const uint16_t* buf, size_t start, size_t count, size_t
         ctx->paint.fakery = mFaces[font_ix].fakery;
         hb_font_t* hbFont = ctx->hbFonts[font_ix];
 #ifdef VERBOSE_DEBUG
-        ALOGD("Run %u, font %d [%d:%d]", run_ix, font_ix, run.start, run.end);
+        ALOGD("Run %zu, font %d [%d:%d]", run_ix, font_ix, run.start, run.end);
 #endif
 
         hb_font_set_ppem(hbFont, size * scaleX, size);
@@ -804,7 +805,7 @@ void Layout::doLayoutRun(const uint16_t* buf, size_t start, size_t count, size_t
                 if (info[i].cluster - start < count) {
                     mAdvances[info[i].cluster - start] += xAdvance;
                 } else {
-                    ALOGE("cluster %d (start %d) out of bounds of count %d",
+                    ALOGE("cluster %zu (start %zu) out of bounds of count %zu",
                         info[i].cluster - start, start, count);
                 }
                 x += xAdvance;
diff --git a/engine/src/flutter/libs/minikin/LineBreaker.cpp b/engine/src/flutter/libs/minikin/LineBreaker.cpp
index a832ca20e26..a2507e0ba87 100644
--- a/engine/src/flutter/libs/minikin/LineBreaker.cpp
+++ b/engine/src/flutter/libs/minikin/LineBreaker.cpp
@@ -249,7 +249,7 @@ void LineBreaker::addWordBreak(size_t offset, ParaWidth preBreak, ParaWidth post
                 cand.penalty = SCORE_DESPERATE;
                 cand.hyphenEdit = 0;
 #if VERBOSE_DEBUG
-                ALOGD("desperate cand: %d %g:%g",
+                ALOGD("desperate cand: %zd %g:%g",
                         mCandidates.size(), cand.postBreak, cand.preBreak);
 #endif
                 addCandidate(cand);
@@ -264,7 +264,7 @@ void LineBreaker::addWordBreak(size_t offset, ParaWidth preBreak, ParaWidth post
     cand.penalty = penalty;
     cand.hyphenEdit = hyph;
 #if VERBOSE_DEBUG
-    ALOGD("cand: %d %g:%g", mCandidates.size(), cand.postBreak, cand.preBreak);
+    ALOGD("cand: %zd %g:%g", mCandidates.size(), cand.postBreak, cand.preBreak);
 #endif
     addCandidate(cand);
 }
@@ -409,7 +409,7 @@ void LineBreaker::computeBreaksOptimal(bool isRectangle) {
         mCandidates[i].prev = bestPrev;
         mCandidates[i].lineNumber = mCandidates[bestPrev].lineNumber + 1;
 #if VERBOSE_DEBUG
-        ALOGD("break %d: score=%g, prev=%d", i, mCandidates[i].score, mCandidates[i].prev);
+        ALOGD("break %zd: score=%g, prev=%zd", i, mCandidates[i].score, mCandidates[i].prev);
 #endif
     }
     finishBreaksOptimal();
diff --git a/engine/src/flutter/libs/minikin/MinikinFontFreeType.cpp b/engine/src/flutter/libs/minikin/MinikinFontFreeType.cpp
index cbeed615932..c9eb456be5f 100644
--- a/engine/src/flutter/libs/minikin/MinikinFontFreeType.cpp
+++ b/engine/src/flutter/libs/minikin/MinikinFontFreeType.cpp
@@ -47,8 +47,8 @@ float MinikinFontFreeType::GetHorizontalAdvance(uint32_t glyph_id,
     return advance * (1.0 / 65536);
 }
 
-void MinikinFontFreeType::GetBounds(MinikinRect* bounds, uint32_t glyph_id,
-    const MinikinPaint& paint) const {
+void MinikinFontFreeType::GetBounds(MinikinRect* /* bounds */, uint32_t /* glyph_id*/,
+        const MinikinPaint& /* paint */) const {
     // TODO: NYI
 }
 
@@ -66,8 +66,8 @@ int32_t MinikinFontFreeType::GetUniqueId() const {
 	return mUniqueId;
 }
 
-bool MinikinFontFreeType::Render(uint32_t glyph_id,
-    const MinikinPaint &paint, GlyphBitmap *result) {
+bool MinikinFontFreeType::Render(uint32_t glyph_id, const MinikinPaint& /* paint */,
+        GlyphBitmap *result) {
     FT_Error error;
     FT_Int32 load_flags = FT_LOAD_DEFAULT;  // TODO: respect hinting settings
     error = FT_Load_Glyph(mTypeface, glyph_id, load_flags);
diff --git a/engine/src/flutter/tests/Android.mk b/engine/src/flutter/tests/Android.mk
index b69b8f243f6..b6bc15c0dcf 100644
--- a/engine/src/flutter/tests/Android.mk
+++ b/engine/src/flutter/tests/Android.mk
@@ -54,4 +54,6 @@ LOCAL_C_INCLUDES := \
     external/libxml2/include \
     external/skia/src/core
 
+LOCAL_CPPFLAGS += -Werror -Wall -Wextra
+
 include $(BUILD_NATIVE_TEST)
diff --git a/engine/src/flutter/tests/HbFaceCacheTest.cpp b/engine/src/flutter/tests/HbFaceCacheTest.cpp
index fbaf0eab150..76eec5b5a83 100644
--- a/engine/src/flutter/tests/HbFaceCacheTest.cpp
+++ b/engine/src/flutter/tests/HbFaceCacheTest.cpp
@@ -35,18 +35,18 @@ public:
     MockMinikinFont(int32_t id) : mId(id) {
     }
 
-    virtual float GetHorizontalAdvance(
-            uint32_t glyph_id, const MinikinPaint &paint) const {
+    virtual float GetHorizontalAdvance(uint32_t /* glyph_id */,
+            const MinikinPaint& /* paint */) const {
         LOG_ALWAYS_FATAL("MockMinikinFont::GetHorizontalAdvance is not implemented.");
         return 0.0f;
     }
 
-    virtual void GetBounds(MinikinRect* bounds, uint32_t glyph_id,
-            const MinikinPaint &paint) const {
+    virtual void GetBounds(MinikinRect* /* bounds */, uint32_t /* glyph_id */,
+            const MinikinPaint& /* paint */) const {
         LOG_ALWAYS_FATAL("MockMinikinFont::GetBounds is not implemented.");
     }
 
-    virtual bool GetTable(uint32_t tag, uint8_t *buf, size_t *size) {
+    virtual bool GetTable(uint32_t /* tag */, uint8_t* /* buf */, size_t* /* size */) {
         LOG_ALWAYS_FATAL("MockMinikinFont::GetTable is not implemented.");
         return false;
     }
diff --git a/engine/src/flutter/tests/MinikinFontForTest.cpp b/engine/src/flutter/tests/MinikinFontForTest.cpp
index 033241e26dc..ed7075188b5 100644
--- a/engine/src/flutter/tests/MinikinFontForTest.cpp
+++ b/engine/src/flutter/tests/MinikinFontForTest.cpp
@@ -29,14 +29,14 @@ MinikinFontForTest::MinikinFontForTest(const std::string& font_path) : mFontPath
 MinikinFontForTest::~MinikinFontForTest() {
 }
 
-float MinikinFontForTest::GetHorizontalAdvance(
-        uint32_t glyph_id, const android::MinikinPaint &paint) const {
+float MinikinFontForTest::GetHorizontalAdvance(uint32_t /* glyph_id */,
+        const android::MinikinPaint& /* paint */) const {
     LOG_ALWAYS_FATAL("MinikinFontForTest::GetHorizontalAdvance is not yet implemented");
     return 0.0f;
 }
 
-void MinikinFontForTest::GetBounds(android::MinikinRect* bounds, uint32_t glyph_id,
-        const android::MinikinPaint& paint) const {
+void MinikinFontForTest::GetBounds(android::MinikinRect* /* bounds */, uint32_t /* glyph_id */,
+        const android::MinikinPaint& /* paint */) const {
     LOG_ALWAYS_FATAL("MinikinFontForTest::GetBounds is not yet implemented");
 }