diff --git a/src/include/ngspice/SIMD/simddef.h b/src/include/ngspice/SIMD/simddef.h
index 42862d050..addadc6ac 100644
--- a/src/include/ngspice/SIMD/simddef.h
+++ b/src/include/ngspice/SIMD/simddef.h
@@ -1,6 +1,8 @@
 #ifndef NG_SIMD_DEF_H
 #define NG_SIMD_DEF_H
 
+#ifndef NSIMD
 #define NSIMD 4
+#endif
 
 #endif