diff --git a/contrib/addtiffo/tif_ovrcache.c b/contrib/addtiffo/tif_ovrcache.c
index 67a88120..ac500ab4 100644
--- a/contrib/addtiffo/tif_ovrcache.c
+++ b/contrib/addtiffo/tif_ovrcache.c
@@ -166,6 +166,7 @@ static void TIFFWriteOvrRow( TIFFOvrCache * psCache )
 /* -------------------------------------------------------------------- */
     nBaseDirOffset = TIFFCurrentDirOffset( psCache->hTIFF );
     nRet = TIFFSetSubDirectory( psCache->hTIFF, psCache->nDirOffset );
+    (void) nRet;
     assert( nRet == 1 );
 
 /* -------------------------------------------------------------------- */
diff --git a/libtiff/tif_jbig.c b/libtiff/tif_jbig.c
index 7ffe8851..a3500e0b 100644
--- a/libtiff/tif_jbig.c
+++ b/libtiff/tif_jbig.c
@@ -199,6 +199,7 @@ static int JBIGEncode(TIFF* tif, uint8* buffer, tmsize_t size, uint16 s)
 
 int TIFFInitJBIG(TIFF* tif, int scheme)
 {
+        (void)scheme;
 	assert(scheme == COMPRESSION_JBIG);
 
 	/*
diff --git a/libtiff/tif_jpeg.c b/libtiff/tif_jpeg.c
index 28d08e37..2c228570 100644
--- a/libtiff/tif_jpeg.c
+++ b/libtiff/tif_jpeg.c
@@ -2482,6 +2482,7 @@ TIFFInitJPEG(TIFF* tif, int scheme)
 {
 	JPEGState* sp;
 
+        (void)scheme;
 	assert(scheme == COMPRESSION_JPEG);
 
 	/*
diff --git a/libtiff/tif_luv.c b/libtiff/tif_luv.c
index 863fc8d7..3bd02e88 100644
--- a/libtiff/tif_luv.c
+++ b/libtiff/tif_luv.c
@@ -193,6 +193,7 @@ LogL16Decode(TIFF* tif, uint8* op, tmsize_t occ, uint16 s)
 	tmsize_t cc;
 	int rc;
 
+        (void)s;
 	assert(s == 0);
 	assert(sp != NULL);
 
@@ -266,6 +267,7 @@ LogLuvDecode24(TIFF* tif, uint8* op, tmsize_t occ, uint16 s)
 	unsigned char* bp;
 	uint32* tp;
 
+        (void)s;
 	assert(s == 0);
 	assert(sp != NULL);
 
@@ -326,6 +328,7 @@ LogLuvDecode32(TIFF* tif, uint8* op, tmsize_t occ, uint16 s)
 	tmsize_t cc;
 	int rc;
 
+        (void)s;
 	assert(s == 0);
 	sp = DecoderState(tif);
 	assert(sp != NULL);
@@ -447,6 +450,7 @@ LogL16Encode(TIFF* tif, uint8* bp, tmsize_t cc, uint16 s)
 	int rc=0, mask;
 	tmsize_t beg;
 
+        (void)s;
 	assert(s == 0);
 	assert(sp != NULL);
 	npixels = cc / sp->pixel_size;
@@ -541,6 +545,7 @@ LogLuvEncode24(TIFF* tif, uint8* bp, tmsize_t cc, uint16 s)
 	uint8* op;
 	uint32* tp;
 
+        (void)s;
 	assert(s == 0);
 	assert(sp != NULL);
 	npixels = cc / sp->pixel_size;
@@ -598,6 +603,7 @@ LogLuvEncode32(TIFF* tif, uint8* bp, tmsize_t cc, uint16 s)
 	int rc=0, mask;
 	tmsize_t beg;
 
+        (void)s;
 	assert(s == 0);
 	assert(sp != NULL);
 
diff --git a/libtiff/tif_lzma.c b/libtiff/tif_lzma.c
index 4e347c94..e150bd63 100644
--- a/libtiff/tif_lzma.c
+++ b/libtiff/tif_lzma.c
@@ -420,6 +420,7 @@ TIFFInitLZMA(TIFF* tif, int scheme)
 	LZMAState* sp;
 	lzma_stream tmp_stream = LZMA_STREAM_INIT;
 
+        (void)scheme;
 	assert( scheme == COMPRESSION_LZMA );
 
 	/*
diff --git a/libtiff/tif_lzw.c b/libtiff/tif_lzw.c
index 3bf92ebd..7bb61078 100644
--- a/libtiff/tif_lzw.c
+++ b/libtiff/tif_lzw.c
@@ -1161,6 +1161,7 @@ int
 TIFFInitLZW(TIFF* tif, int scheme)
 {
 	static const char module[] = "TIFFInitLZW";
+        (void)scheme;
 	assert(scheme == COMPRESSION_LZW);
 	/*
 	 * Allocate state block so tag methods have storage to record values.
diff --git a/libtiff/tif_ojpeg.c b/libtiff/tif_ojpeg.c
index c2d814f0..133d1f1c 100644
--- a/libtiff/tif_ojpeg.c
+++ b/libtiff/tif_ojpeg.c
@@ -421,6 +421,7 @@ TIFFInitOJPEG(TIFF* tif, int scheme)
 	static const char module[]="TIFFInitOJPEG";
 	OJPEGState* sp;
 
+        (void)scheme;
 	assert(scheme==COMPRESSION_OJPEG);
 
         /*
diff --git a/libtiff/tif_open.c b/libtiff/tif_open.c
index 4024b3cd..a0e31583 100644
--- a/libtiff/tif_open.c
+++ b/libtiff/tif_open.c
@@ -104,6 +104,7 @@ TIFFClientOpen(
 		} n;
 		n.a8[0]=1;
 		n.a8[1]=0;
+                (void)n;
 		#ifdef WORDS_BIGENDIAN
 		assert(n.a16==256);
 		#else
diff --git a/libtiff/tif_pixarlog.c b/libtiff/tif_pixarlog.c
index 148ee619..f2912015 100644
--- a/libtiff/tif_pixarlog.c
+++ b/libtiff/tif_pixarlog.c
@@ -1400,6 +1400,7 @@ TIFFInitPixarLog(TIFF* tif, int scheme)
 
 	PixarLogState* sp;
 
+        (void)scheme;
 	assert(scheme == COMPRESSION_PIXARLOG);
 
 	/*
diff --git a/libtiff/tif_webp.c b/libtiff/tif_webp.c
index c7885539..912bc6f0 100644
--- a/libtiff/tif_webp.c
+++ b/libtiff/tif_webp.c
@@ -628,6 +628,7 @@ TIFFInitWebP(TIFF* tif, int scheme)
   static const char module[] = "TIFFInitWebP";
   WebPState* sp;
 
+  (void)scheme;
   assert( scheme == COMPRESSION_WEBP );
 
   /*
diff --git a/test/defer_strile_loading.c b/test/defer_strile_loading.c
index b444c01f..b2280324 100644
--- a/test/defer_strile_loading.c
+++ b/test/defer_strile_loading.c
@@ -148,11 +148,15 @@ int test(int classictif, int height, int tiled)
                     assert(err == 0);
 
                     size = TIFFGetStrileByteCountWithErr(tif, j, &err);
+                    (void)size;
                     assert(size == 256);
                     assert(err == 0);
 
                     fseek(f, offset, SEEK_SET);
-                    fread(inputbuffer, 256, 1, f);
+                    {
+                        size_t nread = fread(inputbuffer, 256, 1, f);
+                        (void)nread;
+                    }
 
                     memset(tilebuffer,0, 256);
                     ret = TIFFReadFromUserBuffer(tif, j,
@@ -204,12 +208,15 @@ int test(int classictif, int height, int tiled)
                     assert(err == 0);
 
                     size = TIFFGetStrileByteCountWithErr(tif, j, &err);
+                    (void)size;
                     assert(size == 1);
                     assert(err == 0);
 
                     fseek(f, offset, SEEK_SET);
-                    fread(inputbuffer, 1, 1, f);
-
+                    {
+                        size_t nread = fread(inputbuffer, 1, 1, f);
+                        (void)nread;
+                    }
                     memset(tilebuffer,0, 1);
                     ret = TIFFReadFromUserBuffer(tif, j,
                                                     inputbuffer, 1,