diff --git a/src/output.cpp b/src/output.cpp
index e1bcd7cdb..19c3533bb 100644
--- a/src/output.cpp
+++ b/src/output.cpp
@@ -402,6 +402,11 @@ int outputter_t::writech(wint_t ch) {
 void outputter_t::writestr(const wchar_t *str) {
     assert(str && "Empty input string");
 
+    if (MB_CUR_MAX == 1) {
+        // Single-byte locale (C/POSIX/ISO-8859).
+        while (*str) writech(*str++);
+        return;
+    }
     size_t len = wcstombs(nullptr, str, 0);  // figure amount of space needed
     if (len == static_cast<size_t>(-1)) {
         debug(3, L"Tried to print invalid wide character string");