diff --git a/test/src/unit-capi-string_dims.cc b/test/src/unit-capi-string_dims.cc
index 9bd483754c9..5f0a2acbd94 100644
--- a/test/src/unit-capi-string_dims.cc
+++ b/test/src/unit-capi-string_dims.cc
@@ -943,7 +943,7 @@ TEST_CASE_METHOD(
   // Create dimension
   tiledb_domain_t* domain;
   tiledb_dimension_t* d;
-  char tmp;
+  char tmp = '\0';
   int rc =
       tiledb_dimension_alloc(ctx_, "d", TILEDB_STRING_ASCII, &tmp, nullptr, &d);
   REQUIRE(rc == TILEDB_ERR);
diff --git a/test/src/unit-cppapi-filter.cc b/test/src/unit-cppapi-filter.cc
index 4b0b1cc3d93..09aca0f5c18 100644
--- a/test/src/unit-cppapi-filter.cc
+++ b/test/src/unit-cppapi-filter.cc
@@ -89,7 +89,7 @@ TEST_CASE("C++ API: Filter options", "[cppapi][filter]") {
   REQUIRE(wrong_type_u == 4);
 
   // Unsupported option
-  uint32_t window;
+  uint32_t window = 1;
   REQUIRE_THROWS_AS(
       f.set_option(TILEDB_BIT_WIDTH_MAX_WINDOW, &window), TileDBError);
   REQUIRE_THROWS_AS(
diff --git a/tiledb/api/c_api/filter/test/unit_capi_filter.cc b/tiledb/api/c_api/filter/test/unit_capi_filter.cc
index 93459cf3d8c..06bc5101524 100644
--- a/tiledb/api/c_api/filter/test/unit_capi_filter.cc
+++ b/tiledb/api/c_api/filter/test/unit_capi_filter.cc
@@ -91,7 +91,7 @@ TEST_CASE(
   REQUIRE(tiledb_status(rc) == TILEDB_OK);
   rc = tiledb_filter_alloc(ctx, TILEDB_FILTER_BZIP2, &filter);
   REQUIRE(tiledb_status(rc) == TILEDB_OK);
-  int value;
+  int value = 0;
   SECTION("null context") {
     rc = tiledb_filter_set_option(
         nullptr, filter, TILEDB_COMPRESSION_LEVEL, &value);