diff --git a/src/runtime/mem_aix.go b/src/runtime/mem_aix.go
index 957aa4dcc2..489d7928e1 100644
--- a/src/runtime/mem_aix.go
+++ b/src/runtime/mem_aix.go
@@ -72,6 +72,7 @@ func sysMap(v unsafe.Pointer, n uintptr, sysStat *sysMemStat) {
 		throw("runtime: out of memory")
 	}
 	if err != 0 {
+		print("runtime: mprotect(", v, ", ", n, ") returned ", err, "\n")
 		throw("runtime: cannot map pages in arena address space")
 	}
 }
diff --git a/src/runtime/mem_bsd.go b/src/runtime/mem_bsd.go
index b152571792..49337eafbf 100644
--- a/src/runtime/mem_bsd.go
+++ b/src/runtime/mem_bsd.go
@@ -73,6 +73,7 @@ func sysMap(v unsafe.Pointer, n uintptr, sysStat *sysMemStat) {
 		throw("runtime: out of memory")
 	}
 	if p != v || err != 0 {
+		print("runtime: mmap(", v, ", ", n, ") returned ", p, ", ", err, "\n")
 		throw("runtime: cannot map pages in arena address space")
 	}
 }
diff --git a/src/runtime/mem_darwin.go b/src/runtime/mem_darwin.go
index 7fccd2bb8e..9f836c0818 100644
--- a/src/runtime/mem_darwin.go
+++ b/src/runtime/mem_darwin.go
@@ -66,6 +66,7 @@ func sysMap(v unsafe.Pointer, n uintptr, sysStat *sysMemStat) {
 		throw("runtime: out of memory")
 	}
 	if p != v || err != 0 {
+		print("runtime: mmap(", v, ", ", n, ") returned ", p, ", ", err, "\n")
 		throw("runtime: cannot map pages in arena address space")
 	}
 }
diff --git a/src/runtime/mem_linux.go b/src/runtime/mem_linux.go
index f8f9c53170..f8333014c2 100644
--- a/src/runtime/mem_linux.go
+++ b/src/runtime/mem_linux.go
@@ -189,6 +189,7 @@ func sysMap(v unsafe.Pointer, n uintptr, sysStat *sysMemStat) {
 		throw("runtime: out of memory")
 	}
 	if p != v || err != 0 {
+		print("runtime: mmap(", v, ", ", n, ") returned ", p, ", ", err, "\n")
 		throw("runtime: cannot map pages in arena address space")
 	}
 }