diff --git a/src/string/memmem.c b/src/string/memmem.c
index 58a21fcd6e8dd36ee0370ad907da635397e912a6..11eff86e443e73d5490124f641ce1653f34f53e4 100644
--- a/src/string/memmem.c
+++ b/src/string/memmem.c
@@ -12,8 +12,8 @@ static char *twobyte_memmem(const unsigned char *h, size_t k, const unsigned cha
 
 static char *threebyte_memmem(const unsigned char *h, size_t k, const unsigned char *n)
 {
-	uint32_t nw = n[0]<<24 | n[1]<<16 | n[2]<<8;
-	uint32_t hw = h[0]<<24 | h[1]<<16 | h[2]<<8;
+	uint32_t nw = (uint32_t)n[0]<<24 | n[1]<<16 | n[2]<<8;
+	uint32_t hw = (uint32_t)h[0]<<24 | h[1]<<16 | h[2]<<8;
 	for (h+=3, k-=3; k; k--, hw = (hw|*h++)<<8)
 		if (hw == nw) return (char *)h-3;
 	return hw == nw ? (char *)h-3 : 0;
@@ -21,8 +21,8 @@ static char *threebyte_memmem(const unsigned char *h, size_t k, const unsigned c
 
 static char *fourbyte_memmem(const unsigned char *h, size_t k, const unsigned char *n)
 {
-	uint32_t nw = n[0]<<24 | n[1]<<16 | n[2]<<8 | n[3];
-	uint32_t hw = h[0]<<24 | h[1]<<16 | h[2]<<8 | h[3];
+	uint32_t nw = (uint32_t)n[0]<<24 | n[1]<<16 | n[2]<<8 | n[3];
+	uint32_t hw = (uint32_t)h[0]<<24 | h[1]<<16 | h[2]<<8 | h[3];
 	for (h+=4, k-=4; k; k--, hw = hw<<8 | *h++)
 		if (hw == nw) return (char *)h-4;
 	return hw == nw ? (char *)h-4 : 0;
diff --git a/src/string/strstr.c b/src/string/strstr.c
index 55ba1c7b45a0ef0b7087754684055aa0e84d27ce..43a0207a725be2a04af3b3cc6390a214aaae0995 100644
--- a/src/string/strstr.c
+++ b/src/string/strstr.c
@@ -10,16 +10,16 @@ static char *twobyte_strstr(const unsigned char *h, const unsigned char *n)
 
 static char *threebyte_strstr(const unsigned char *h, const unsigned char *n)
 {
-	uint32_t nw = n[0]<<24 | n[1]<<16 | n[2]<<8;
-	uint32_t hw = h[0]<<24 | h[1]<<16 | h[2]<<8;
+	uint32_t nw = (uint32_t)n[0]<<24 | n[1]<<16 | n[2]<<8;
+	uint32_t hw = (uint32_t)h[0]<<24 | h[1]<<16 | h[2]<<8;
 	for (h+=2; *h && hw != nw; hw = (hw|*++h)<<8);
 	return *h ? (char *)h-2 : 0;
 }
 
 static char *fourbyte_strstr(const unsigned char *h, const unsigned char *n)
 {
-	uint32_t nw = n[0]<<24 | n[1]<<16 | n[2]<<8 | n[3];
-	uint32_t hw = h[0]<<24 | h[1]<<16 | h[2]<<8 | h[3];
+	uint32_t nw = (uint32_t)n[0]<<24 | n[1]<<16 | n[2]<<8 | n[3];
+	uint32_t hw = (uint32_t)h[0]<<24 | h[1]<<16 | h[2]<<8 | h[3];
 	for (h+=3; *h && hw != nw; hw = hw<<8 | *++h);
 	return *h ? (char *)h-3 : 0;
 }