--- a/testsuite/ltrace.main/system_calls.exp
+++ b/testsuite/ltrace.main/system_calls.exp
@@ -29,8 +29,10 @@ if [regexp {ELF from incompatible architecture} $exec_output] {
 }
 
 
-set pattern "SYS_munmap"
-ltrace_verify_output ${objdir}/${subdir}/${testfile}.ltrace $pattern 2
+## disabled in Gentoo: libc's stdio tends to call (or not to call) munmap
+## depending on heuristics of stdio buffer sizes.
+##set pattern "SYS_munmap"
+##ltrace_verify_output ${objdir}/${subdir}/${testfile}.ltrace $pattern 2
 set pattern "SYS_write"
 ltrace_verify_output ${objdir}/${subdir}/${testfile}.ltrace $pattern 1
 set pattern "SYS_unlink"