diff --git a/pw_blob_store/size_report/base.cc b/pw_blob_store/size_report/base.cc
index 85ffa1a413..1cecd10cdb 100644
--- a/pw_blob_store/size_report/base.cc
+++ b/pw_blob_store/size_report/base.cc
@@ -51,7 +51,7 @@ int main() {
   PW_LOG_INFO("We care about optimizing: %d", *unoptimizable);
 
   void* result =
-      std::memset((void*)working_buffer, sizeof(working_buffer), 0x55);
+      std::memset((void*)working_buffer, 0x55, sizeof(working_buffer));
   is_set = (result != nullptr);
 
   {
diff --git a/pw_blob_store/size_report/basic_blob.cc b/pw_blob_store/size_report/basic_blob.cc
index a2ea6106c4..80e6650b69 100644
--- a/pw_blob_store/size_report/basic_blob.cc
+++ b/pw_blob_store/size_report/basic_blob.cc
@@ -55,7 +55,7 @@ int main() {
   PW_LOG_INFO("We care about optimizing: %d", *unoptimizable);
 
   void* result =
-      std::memset((void*)working_buffer, sizeof(working_buffer), 0x55);
+      std::memset((void*)working_buffer, 0x55, sizeof(working_buffer));
   is_set = (result != nullptr);
 
   {
diff --git a/pw_blob_store/size_report/deferred_write_blob.cc b/pw_blob_store/size_report/deferred_write_blob.cc
index 948c5ae01c..1f53c93dbc 100644
--- a/pw_blob_store/size_report/deferred_write_blob.cc
+++ b/pw_blob_store/size_report/deferred_write_blob.cc
@@ -55,7 +55,7 @@ int main() {
   PW_LOG_INFO("We care about optimizing: %d", *unoptimizable);
 
   void* result =
-      std::memset((void*)working_buffer, sizeof(working_buffer), 0x55);
+      std::memset((void*)working_buffer, 0x55, sizeof(working_buffer));
   is_set = (result != nullptr);
 
   {