diff --git a/src/include/OpenImageIO/hash.h b/src/include/OpenImageIO/hash.h
index 8b52cf8a51..87de1db3b8 100644
--- a/src/include/OpenImageIO/hash.h
+++ b/src/include/OpenImageIO/hash.h
@@ -80,7 +80,12 @@ inline uint64_t fasthash64(const void *buf, size_t len, uint64_t seed=1771)
 	uint64_t v;
 
 	while (pos != end) {
+		// This appears to be a false positive which only affects GCC.
+		// https://godbolt.org/z/5q7Y7ndfb
+		OIIO_PRAGMA_WARNING_PUSH
+		OIIO_GCC_ONLY_PRAGMA(GCC diagnostic ignored "-Wmaybe-uninitialized")
 		v  = *pos++;
+		OIIO_PRAGMA_WARNING_PUSH
 		h ^= mix(v);
 		h *= m;
 	}
diff --git a/src/libtexture/imagecache_pvt.h b/src/libtexture/imagecache_pvt.h
index a9dd81e476..e9c79aa0f6 100644
--- a/src/libtexture/imagecache_pvt.h
+++ b/src/libtexture/imagecache_pvt.h
@@ -560,13 +560,17 @@ struct TileID {
     /// Digest the TileID into a size_t to use as a hash key.
     size_t hash() const
     {
-        const uint64_t a = (uint64_t(m_x) << 32) + uint64_t(m_y);
-        const uint64_t b = (uint64_t(m_z) << 32) + uint64_t(m_subimage);
-        const uint64_t c = (uint64_t(m_miplevel) << 32)
-                           + (uint64_t(m_chbegin) << 16) + uint64_t(m_chend);
-        const uint64_t d = m_file->filename().hash()
-                           + uint64_t(m_colortransformid);
-        return fasthash::fasthash64({ a, b, c, d });
+        static constexpr size_t member_size
+            = sizeof(m_x) + sizeof(m_y) + sizeof(m_z) + sizeof(m_subimage)
+              + sizeof(m_miplevel) + sizeof(m_chbegin) + sizeof(m_chend)
+              + sizeof(m_colortransformid) + sizeof(m_padding) + sizeof(m_file);
+        static_assert(
+            sizeof(*this) == member_size,
+            "All TileID members must be accounted for so we can hash the entire class.");
+        static_assert(
+            sizeof(*this) % sizeof(uint64_t) == 0,
+            "FastHash uses the fewest instructions when data size is a multiple of 8 bytes.");
+        return fasthash::fasthash64(this, sizeof(*this));
     }
 
     /// Functor that hashes a TileID
@@ -590,6 +594,7 @@ struct TileID {
     int m_miplevel;            ///< MIP-map level
     short m_chbegin, m_chend;  ///< Channel range
     int m_colortransformid;    ///< Colorspace id (0 == default)
+    int m_padding = 0;         ///< Unused
     ImageCacheFile* m_file;    ///< Which ImageCacheFile we refer to
 };