diff --git a/code/libspeex/config.h b/code/libspeex/config.h
index abd35f09..e6657fc0 100644
--- a/code/libspeex/config.h
+++ b/code/libspeex/config.h
@@ -6,6 +6,9 @@
 // SSE is enabled.
 #ifndef _USE_SSE
 #  define USE_ALLOCA
+#  if defined(__sun)  /* Solaris needs this for alloca(). */
+#    define HAVE_ALLOCA_H
+#  endif
 #endif
 
 /* Default to floating point */