diff --git a/ci/lib.sh b/ci/lib.sh
index c6ccbf8c17..db593cc62c 100755
--- a/ci/lib.sh
+++ b/ci/lib.sh
@@ -227,7 +227,6 @@ then
 	cache_dir="$HOME/none"
 
 	GIT_TEST_OPTS="--github-workflow-markup"
-	JOBS=10
 
 	distro=$(echo "$CI_JOB_IMAGE" | tr : -)
 elif test true = "$GITLAB_CI"
@@ -250,7 +249,6 @@ then
 	case "$OS,$CI_JOB_IMAGE" in
 	Windows_NT,*)
 		CI_OS_NAME=windows
-		JOBS=$NUMBER_OF_PROCESSORS
 		;;
 	*,macos-*)
 		# GitLab CI has Python installed via multiple package managers,
@@ -260,11 +258,9 @@ then
 		export PATH="$(brew --prefix)/bin:$PATH"
 
 		CI_OS_NAME=osx
-		JOBS=$(nproc)
 		;;
 	*,almalinux:*|*,alpine:*|*,debian:*|*,fedora:*|*,ubuntu:*|*,i386/ubuntu:*)
 		CI_OS_NAME=linux
-		JOBS=$(nproc)
 		;;
 	*)
 		echo "Could not identify OS image" >&2
@@ -291,6 +287,18 @@ else
 	exit 1
 fi
 
+case "$CI_OS_NAME" in
+windows|windows_nt)
+	JOBS=$NUMBER_OF_PROCESSORS
+	;;
+osx)
+	JOBS=$(sysctl -n hw.logicalcpu)
+	;;
+*)
+	JOBS=$(nproc)
+	;;
+esac
+
 MAKEFLAGS="$MAKEFLAGS --jobs=$JOBS"
 GIT_PROVE_OPTS="--timer --jobs $JOBS"
 
diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh
index 4be5c51489..01b97c8888 100755
--- a/t/t4205-log-pretty-formats.sh
+++ b/t/t4205-log-pretty-formats.sh
@@ -1189,7 +1189,7 @@ test_expect_success EXPENSIVE,SIZE_T_IS_64BIT 'set up huge commit' '
 test_expect_success EXPENSIVE,SIZE_T_IS_64BIT 'log --pretty with huge commit message' '
 	git log -1 --format="%B%<(1)%x30" $huge_commit >actual &&
 	echo 0 >>expect &&
-	test_cmp expect actual
+	test_cmp_bin expect actual
 '
 
 test_expect_success EXPENSIVE,SIZE_T_IS_64BIT 'log --pretty with huge commit message does not cause allocation failure' '