diff --git a/data/supported-extensions b/data/supported-extensions
index 3192f05..0eda615 100644
--- a/data/supported-extensions
+++ b/data/supported-extensions
@@ -1,5 +1,5 @@
 amqp 5.6 7.0 7.1 7.2 7.3
-apcu 7.0 7.1 7.2 7.3
+apcu 5.6 7.0 7.1 7.2 7.3
 bcmath 5.6 7.0 7.1 7.2 7.3
 bz2 5.6 7.0 7.1 7.2 7.3
 calendar 5.6 7.0 7.1 7.2 7.3
diff --git a/install-php-extensions b/install-php-extensions
index 14376a9..632247b 100755
--- a/install-php-extensions
+++ b/install-php-extensions
@@ -48,7 +48,7 @@ getPHPInstalledModules () {
 			Zend\ OPcache)
 				getPHPInstalledModules_moduleNormalized='opcache'
 				;;
-			*\ *|A*|*B*|*C*|*D*|*E*|*F*|*G*|*H*|*I*|*J*|*K*|*L*|*M*|*N*|*O*|*P*|*Q*|*R*|*S*|*T*|*U*|*V*|*W*|*X*|*Y*|*Z*)
+			*\ *|*A*|*B*|*C*|*D*|*E*|*F*|*G*|*H*|*I*|*J*|*K*|*L*|*M*|*N*|*O*|*P*|*Q*|*R*|*S*|*T*|*U*|*V*|*W*|*X*|*Y*|*Z*)
 				printf '### WARNING Unrecognized module name: %s ###\n' "${getPHPInstalledModules_module}" >&2
 				;;
 			*)
@@ -425,6 +425,11 @@ installPECLModule () {
 	installPECLModule_actual="${2}"
 	installPECLModule_stdin=''
 	case "${2}" in
+		apcu)
+			if test $1 -le 506; then
+				installPECLModule_actual="${2}-4.0.11"
+			fi
+			;;
 		mcrypt)
 			if test $1 -ge 702; then
 				installPECLModule_stdin='autodetect'