diff --git a/src/libgit2/CMakeLists.txt b/src/libgit2/CMakeLists.txt
index c2a97e1..8c5b2ea 100644
--- a/src/libgit2/CMakeLists.txt
+++ b/src/libgit2/CMakeLists.txt
@@ -2,7 +2,7 @@
 # git library functionality.
 
 add_library(libgit2 OBJECT)
-set_target_properties(libgit2 PROPERTIES C_STANDARD 90)
+set_target_properties(libgit2 PROPERTIES C_STANDARD 99)
 set_target_properties(libgit2 PROPERTIES C_EXTENSIONS OFF)
 
 include(PkgBuildConfig)
diff --git a/src/util/CMakeLists.txt b/src/util/CMakeLists.txt
index ee35eb9..158fac2 100644
--- a/src/util/CMakeLists.txt
+++ b/src/util/CMakeLists.txt
@@ -1,7 +1,7 @@
 # util: a shared library for common utility functions for libgit2 projects
 
 add_library(util OBJECT)
-set_target_properties(util PROPERTIES C_STANDARD 90)
+set_target_properties(util PROPERTIES C_STANDARD 99)
 set_target_properties(util PROPERTIES C_EXTENSIONS OFF)
 
 configure_file(git2_features.h.in git2_features.h)
