diff --git a/examples/primes.cpp b/examples/primes.cpp
index a3e871a..e5ee4f0 100644
--- a/examples/primes.cpp
+++ b/examples/primes.cpp
@@ -23,6 +23,7 @@
 #include <vector>
 
 #include <math.h>
+#include <stdio.h>
 
 // searchMax defines the upper limit on primes to find.
 constexpr int searchMax = 10000000;
diff --git a/kokoro/ubuntu/docker.sh b/kokoro/ubuntu/docker.sh
index 4cba967..e4902ef 100755
--- a/kokoro/ubuntu/docker.sh
+++ b/kokoro/ubuntu/docker.sh
@@ -29,7 +29,7 @@ function status {
 . /bin/using.sh # Declare the bash `using` function for configuring toolchains.
 
 status "Setting up environment"
-using gcc-9 # Always update gcc so we get a newer standard library.
+using gcc-10 # Always update gcc so we get a newer standard library.
 
 if [ "$BUILD_SYSTEM" == "cmake" ]; then
     using cmake-3.17.2