diff --git a/src/dsp/alpha_processing_mips_dsp_r2.c b/src/dsp/alpha_processing_mips_dsp_r2.c
index 186e9e03..e5644998 100644
--- a/src/dsp/alpha_processing_mips_dsp_r2.c
+++ b/src/dsp/alpha_processing_mips_dsp_r2.c
@@ -124,16 +124,19 @@ static void MultARGBRow(uint32_t* const ptr, int width, int inverse) {
   }
 }
 
-#endif  // WEBP_USE_MIPS_DSP_R2
-
 //------------------------------------------------------------------------------
-// Init function
+// Entry point
 
 extern void WebPInitAlphaProcessingMIPSdspR2(void);
 
 WEBP_TSAN_IGNORE_FUNCTION void WebPInitAlphaProcessingMIPSdspR2(void) {
-#if defined(WEBP_USE_MIPS_DSP_R2)
   WebPDispatchAlpha = DispatchAlpha;
   WebPMultARGBRow = MultARGBRow;
-#endif
 }
+
+#else  // !WEBP_USE_MIPS_DSP_R2
+
+extern void WebPInitAlphaProcessingMIPSdspR2(void);
+WEBP_TSAN_IGNORE_FUNCTION void WebPInitAlphaProcessingMIPSdspR2(void) {}
+
+#endif  // WEBP_USE_MIPS_DSP_R2
diff --git a/src/dsp/alpha_processing_sse2.c b/src/dsp/alpha_processing_sse2.c
index 9233246c..40501303 100644
--- a/src/dsp/alpha_processing_sse2.c
+++ b/src/dsp/alpha_processing_sse2.c
@@ -277,20 +277,23 @@ static void MultRow(uint8_t* const ptr, const uint8_t* const alpha,
   if (width > 0) WebPMultRowC(ptr + x, alpha + x, width, inverse);
 }
 
-#endif   // WEBP_USE_SSE2
-
 //------------------------------------------------------------------------------
-// Init function
+// Entry point
 
 extern void WebPInitAlphaProcessingSSE2(void);
 
 WEBP_TSAN_IGNORE_FUNCTION void WebPInitAlphaProcessingSSE2(void) {
-#if defined(WEBP_USE_SSE2)
   WebPMultARGBRow = MultARGBRow;
   WebPMultRow = MultRow;
   WebPApplyAlphaMultiply = ApplyAlphaMultiply;
   WebPDispatchAlpha = DispatchAlpha;
   WebPDispatchAlphaToGreen = DispatchAlphaToGreen;
   WebPExtractAlpha = ExtractAlpha;
-#endif
 }
+
+#else  // !WEBP_USE_SSE2
+
+extern void WebPInitAlphaProcessingSSE2(void);
+WEBP_TSAN_IGNORE_FUNCTION void WebPInitAlphaProcessingSSE2(void) {}
+
+#endif  // WEBP_USE_SSE2