diff --git a/src/pulse/proplist.c b/src/pulse/proplist.c
index a0913b109..91351159c 100644
--- a/src/pulse/proplist.c
+++ b/src/pulse/proplist.c
@@ -674,7 +674,7 @@ int pa_proplist_isempty(const pa_proplist *p) {
     return pa_hashmap_isempty(MAKE_HASHMAP_CONST(p));
 }
 
-int pa_proplist_equal(pa_proplist *a, pa_proplist *b) {
+int pa_proplist_equal(const pa_proplist *a, const pa_proplist *b) {
     const void *key = NULL;
     struct property *a_prop = NULL;
     struct property *b_prop = NULL;
diff --git a/src/pulse/proplist.h b/src/pulse/proplist.h
index 2c99976f6..e50518b37 100644
--- a/src/pulse/proplist.h
+++ b/src/pulse/proplist.h
@@ -404,7 +404,7 @@ int pa_proplist_isempty(const pa_proplist *p);
 
 /** Return non-zero when a and b have the same keys and values.
  * \since 0.9.16 */
-int pa_proplist_equal(pa_proplist *a, pa_proplist *b);
+int pa_proplist_equal(const pa_proplist *a, const pa_proplist *b);
 
 PA_C_DECL_END