diff --git a/src/halfvec.c b/src/halfvec.c
index b1400dd..1781100 100644
--- a/src/halfvec.c
+++ b/src/halfvec.c
@@ -32,7 +32,7 @@
 #endif
 
 #define STATE_DIMS(x) (ARR_DIMS(x)[0] - 1)
-#define CreateStateDatums(dim) palloc_array(Datum, (dim + 1))
+#define CreateStateDatums(dim) palloc_array(Datum, (dim) + 1)
 
 /*
  * Get a half from a message buffer
diff --git a/src/vector.c b/src/vector.c
index 09ecf9c..dc13397 100644
--- a/src/vector.c
+++ b/src/vector.c
@@ -35,7 +35,7 @@
 #endif
 
 #define STATE_DIMS(x) (ARR_DIMS(x)[0] - 1)
-#define CreateStateDatums(dim) palloc_array(Datum, (dim + 1))
+#define CreateStateDatums(dim) palloc_array(Datum, (dim) + 1)
 
 #if defined(USE_TARGET_CLONES) && !defined(__FMA__)
 #define VECTOR_TARGET_CLONES __attribute__((target_clones("default", "fma")))