diff --git a/src/util/env.c b/src/util/env.c
index 4b753ab87..c4e9688fc 100644
--- a/src/util/env.c
+++ b/src/util/env.c
@@ -24,7 +24,7 @@
  * set @a name to specified substring of @a value.
  */
 int
-env_set(char *name, char *value, int length)
+env_set(const char *name, char *value, int length)
 {
 	int true_length, substring = 0;
 
diff --git a/src/util/env.h b/src/util/env.h
index a607ed44c..1af1087f7 100644
--- a/src/util/env.h
+++ b/src/util/env.h
@@ -5,7 +5,7 @@
 extern "C" {
 #endif
 
-int env_set(char *name, char *value, int len);
+int env_set(const char *name, char *value, int len);
 
 #ifdef __cplusplus
 }