diff --git a/CMakeLists.txt b/CMakeLists.txt
index 11bb31892c..ee9f9c2817 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -426,8 +426,8 @@ set(ZIG_SOURCES
     "${CMAKE_SOURCE_DIR}/src/util.cpp"
     "${CMAKE_SOURCE_DIR}/src/translate_c.cpp"
 )
-set(ZIG_SOURCES_O3
-    "${CMAKE_SOURCE_DIR}/src/blake2b.cpp"
+set(BLAKE_SOURCES
+    "${CMAKE_SOURCE_DIR}/src/blake2b.c"
 )
 set(ZIG_CPP_SOURCES
     "${CMAKE_SOURCE_DIR}/src/zig_llvm.cpp"
@@ -795,6 +795,7 @@ else()
   set(EXE_CFLAGS "${EXE_CFLAGS} -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -D_GNU_SOURCE -fno-exceptions -fno-rtti  -Werror=strict-prototypes -Werror=old-style-definition -Werror=type-limits -Wno-missing-braces")
 endif()
 
+set(BLAKE_CFLAGS "-std=c99")
 
 set(EXE_LDFLAGS " ")
 if(MINGW)
@@ -816,9 +817,9 @@ set_target_properties(zig_cpp PROPERTIES
     COMPILE_FLAGS ${EXE_CFLAGS}
 )
 
-add_library(zig_O3 STATIC ${ZIG_SOURCES_O3})
-set_target_properties(zig_O3 PROPERTIES
-    COMPILE_FLAGS "${EXE_CFLAGS} -O3"
+add_library(embedded_blake STATIC ${BLAKE_SOURCES})
+set_target_properties(embedded_blake PROPERTIES
+    COMPILE_FLAGS "${BLAKE_CFLAGS} -O3"
 )
 
 add_executable(zig ${ZIG_SOURCES})
@@ -829,7 +830,7 @@ set_target_properties(zig PROPERTIES
 
 target_link_libraries(zig LINK_PUBLIC
     zig_cpp
-    zig_O3
+    embedded_blake
     ${SOFTFLOAT_LIBRARIES}
     ${CLANG_LIBRARIES}
     ${LLD_LIBRARIES}
diff --git a/src/blake2b.cpp b/src/blake2b.c
similarity index 100%
rename from src/blake2b.cpp
rename to src/blake2b.c