diff --git a/lib/cmock_generator_utils.rb b/lib/cmock_generator_utils.rb
index 88064d8..24959ce 100644
--- a/lib/cmock_generator_utils.rb
+++ b/lib/cmock_generator_utils.rb
@@ -38,6 +38,7 @@ class CMockGeneratorUtils
     lines =  "  CMOCK_MEM_INDEX_TYPE cmock_guts_index = CMock_Guts_MemNew(sizeof(CMOCK_#{func_name}_CALL_INSTANCE));\n"
     lines << "  CMOCK_#{func_name}_CALL_INSTANCE* cmock_call_instance = (CMOCK_#{func_name}_CALL_INSTANCE*)CMock_Guts_GetAddressFor(cmock_guts_index);\n"
     lines << "  UNITY_TEST_ASSERT_NOT_NULL(cmock_call_instance, cmock_line, \"CMock has run out of memory. Please allocate more.\");\n"
+    lines << "  memset(cmock_call_instance, 0, sizeof(*cmock_call_instance));\n"
     lines << "  Mock.#{func_name}_CallInstance = CMock_Guts_MemChain(Mock.#{func_name}_CallInstance, cmock_guts_index);\n"
     lines << "  Mock.#{func_name}_IgnoreBool = (int)0;\n" if (@ignore)
     lines << "  cmock_call_instance->LineNumber = cmock_line;\n"
diff --git a/test/unit/cmock_generator_utils_test.rb b/test/unit/cmock_generator_utils_test.rb
index e82cfff..917b32c 100644
--- a/test/unit/cmock_generator_utils_test.rb
+++ b/test/unit/cmock_generator_utils_test.rb
@@ -62,6 +62,7 @@ class CMockGeneratorUtilsTest < Test::Unit::TestCase
       "  CMOCK_MEM_INDEX_TYPE cmock_guts_index = CMock_Guts_MemNew(sizeof(CMOCK_Apple_CALL_INSTANCE));\n" +
       "  CMOCK_Apple_CALL_INSTANCE* cmock_call_instance = (CMOCK_Apple_CALL_INSTANCE*)CMock_Guts_GetAddressFor(cmock_guts_index);\n" +
       "  UNITY_TEST_ASSERT_NOT_NULL(cmock_call_instance, cmock_line, \"CMock has run out of memory. Please allocate more.\");\n" +
+      "  memset(cmock_call_instance, 0, sizeof(*cmock_call_instance));\n" +
       "  Mock.Apple_CallInstance = CMock_Guts_MemChain(Mock.Apple_CallInstance, cmock_guts_index);\n" +
       "  cmock_call_instance->LineNumber = cmock_line;\n"
     output = @cmock_generator_utils_simple.code_add_base_expectation("Apple")
@@ -73,6 +74,7 @@ class CMockGeneratorUtilsTest < Test::Unit::TestCase
       "  CMOCK_MEM_INDEX_TYPE cmock_guts_index = CMock_Guts_MemNew(sizeof(CMOCK_Apple_CALL_INSTANCE));\n" +
       "  CMOCK_Apple_CALL_INSTANCE* cmock_call_instance = (CMOCK_Apple_CALL_INSTANCE*)CMock_Guts_GetAddressFor(cmock_guts_index);\n" +
       "  UNITY_TEST_ASSERT_NOT_NULL(cmock_call_instance, cmock_line, \"CMock has run out of memory. Please allocate more.\");\n" +
+      "  memset(cmock_call_instance, 0, sizeof(*cmock_call_instance));\n" +
       "  Mock.Apple_CallInstance = CMock_Guts_MemChain(Mock.Apple_CallInstance, cmock_guts_index);\n" +
       "  Mock.Apple_IgnoreBool = (int)0;\n" +
       "  cmock_call_instance->LineNumber = cmock_line;\n" +
@@ -87,6 +89,7 @@ class CMockGeneratorUtilsTest < Test::Unit::TestCase
       "  CMOCK_MEM_INDEX_TYPE cmock_guts_index = CMock_Guts_MemNew(sizeof(CMOCK_Apple_CALL_INSTANCE));\n" +
       "  CMOCK_Apple_CALL_INSTANCE* cmock_call_instance = (CMOCK_Apple_CALL_INSTANCE*)CMock_Guts_GetAddressFor(cmock_guts_index);\n" +
       "  UNITY_TEST_ASSERT_NOT_NULL(cmock_call_instance, cmock_line, \"CMock has run out of memory. Please allocate more.\");\n" +
+      "  memset(cmock_call_instance, 0, sizeof(*cmock_call_instance));\n" +
       "  Mock.Apple_CallInstance = CMock_Guts_MemChain(Mock.Apple_CallInstance, cmock_guts_index);\n" +
       "  Mock.Apple_IgnoreBool = (int)0;\n" +
       "  cmock_call_instance->LineNumber = cmock_line;\n" +