diff --git a/var/spack/repos/builtin/packages/cairo/package.py b/var/spack/repos/builtin/packages/cairo/package.py
index ddb8d2fd03..b2911e126a 100644
--- a/var/spack/repos/builtin/packages/cairo/package.py
+++ b/var/spack/repos/builtin/packages/cairo/package.py
@@ -37,6 +37,7 @@ class Cairo(Package):
     depends_on("glib")
     depends_on("pixman")
     depends_on("freetype")
+    depends_on("pkg-config", type="build")
     depends_on("fontconfig@2.10.91:")  # Require newer version of fontconfig.
 
     def install(self, spec, prefix):
diff --git a/var/spack/repos/builtin/packages/pixman/package.py b/var/spack/repos/builtin/packages/pixman/package.py
index 3d7e332a3f..39041587f5 100644
--- a/var/spack/repos/builtin/packages/pixman/package.py
+++ b/var/spack/repos/builtin/packages/pixman/package.py
@@ -34,6 +34,7 @@ class Pixman(Package):
 
     version('0.32.6', '3a30859719a41bd0f5cccffbfefdd4c2')
 
+    depends_on("pkg-config", type="build")
     depends_on("libpng")
 
     def install(self, spec, prefix):