diff --git a/src/sha1.c b/src/sha1.c
index ec4cb6c..9c0ea9c 100644
--- a/src/sha1.c
+++ b/src/sha1.c
@@ -102,7 +102,7 @@ A million repetitions of "a"
 
 #include "sha1.h"
 
-void SHA1_Transform(uint32_t state[5], const uint8_t buffer[64]);
+static void SHA1_Transform(uint32_t state[5], const uint8_t buffer[64]);
 
 #define rol(value, bits) (((value) << (bits)) | ((value) >> (32 - (bits))))
 
@@ -140,7 +140,7 @@ void SHAPrintContext(SHA1_CTX *context, char *msg){
 #endif /* VERBOSE */
 
 /* Hash a single 512-bit block. This is the core of the algorithm. */
-void SHA1_Transform(uint32_t state[5], const uint8_t buffer[64])
+static void SHA1_Transform(uint32_t state[5], const uint8_t buffer[64])
 {
     uint32_t a, b, c, d, e;
     typedef union {
diff --git a/src/sha1.h b/src/sha1.h
index b637f66..349e851 100644
--- a/src/sha1.h
+++ b/src/sha1.h
@@ -20,6 +20,11 @@ typedef struct {
 
 #define SHA1_DIGEST_SIZE 20
 
+/* prevent name collisions with libcrypto */
+#define SHA1_Init   xmpp_SHA1_Init
+#define SHA1_Update xmpp_SHA1_Update
+#define SHA1_Final  xmpp_SHA1_Final
+
 void SHA1_Init(SHA1_CTX* context);
 void SHA1_Update(SHA1_CTX* context, const uint8_t* data, const size_t len);
 void SHA1_Final(SHA1_CTX* context, uint8_t digest[SHA1_DIGEST_SIZE]);