diff --git a/pyfastani/_sequtils/sequtils.cpp b/pyfastani/_sequtils/sequtils.cpp
index a08c7da2e3041856e7c3a827d2546c32cbfcebe6..1946c0c8a86618bb8507cc5af7198cb10db81146 100644
--- a/pyfastani/_sequtils/sequtils.cpp
+++ b/pyfastani/_sequtils/sequtils.cpp
@@ -41,19 +41,25 @@ extern "C" {
 
     void copy_upper(char* dst, const char* src, size_t len) {
         #ifdef __arm__
+        #ifdef NEON_BUILD_SUPPORTED
           if (features.neon)
             return neon_copy_upper(dst, src, len);
           else
         #endif
+        #endif
         #ifdef __aarch64__
+        #ifdef NEON_BUILD_SUPPORTED
           if (features.neon)
             return neon_copy_upper(dst, src, len);
           else
         #endif
+        #endif
         #if defined(__x86__) || defined(__x86_64__)
+        #ifdef SSE2_BUILD_SUPPORTED
           if (features.sse2)
             return sse2_copy_upper(dst, src, len); // fast copying plus upper.
           else
+        #endif
         #endif
             return default_copy_upper(dst, src, len);
     }
@@ -76,9 +82,11 @@ extern "C" {
 
     void reverse_complement(char* dst, const char* src, size_t len) {
         #if defined(__x86__) || defined(__x86_64__)
+        #ifdef SSSE3_BUILD_SUPPORTED
           if (features.ssse3)
             return ssse3_reverse_complement(dst, src, len); // fast reverse complement.
           else
+        #endif
         #endif
             return default_reverse_complement(dst, src, len);
     }