diff --git a/src/api/api_stats.cpp b/src/api/api_stats.cpp
index a6569e878..b39c8368a 100644
--- a/src/api/api_stats.cpp
+++ b/src/api/api_stats.cpp
@@ -130,7 +130,7 @@ extern "C" {
         Z3_CATCH_RETURN(0.0);
     }
 
-    unsigned long long Z3_API Z3_get_estimated_alloc_size(void) {
+    __uint64 Z3_API Z3_get_estimated_alloc_size(void) {
         return memory::get_allocation_size();
     }
 
diff --git a/src/api/z3_api.h b/src/api/z3_api.h
index f8cc2d64e..b37c963b4 100644
--- a/src/api/z3_api.h
+++ b/src/api/z3_api.h
@@ -5970,9 +5970,9 @@ extern "C" {
     /**
     \brief Return the estimated allocated memory in bytes.
 
-    def_API('Z3_get_estimated_alloc_size', ULLONG, ())
+    def_API('Z3_get_estimated_alloc_size', UINT64, ())
     */
-    unsigned long long Z3_API Z3_get_estimated_alloc_size(void);
+    __uint64 Z3_API Z3_get_estimated_alloc_size(void);
 
     /*@}*/