diff --git a/distrho/extra/String.hpp b/distrho/extra/String.hpp
index 7364662d..3f16895c 100644
--- a/distrho/extra/String.hpp
+++ b/distrho/extra/String.hpp
@@ -695,7 +695,7 @@ public:
             "abcdefghijklmnopqrstuvwxyz"
             "0123456789+/";
 
-        const size_t strBufSize = std::min(d_nextPowerOf2(static_cast<uint32_t>(dataSize/3)), 65536U);
+        const size_t strBufSize = std::min(d_nextPowerOf2(static_cast<uint32_t>(dataSize / 3) + 1), 65536U);
         char* strBuf = static_cast<char*>(std::malloc(strBufSize));
         DISTRHO_SAFE_ASSERT_RETURN(strBuf != nullptr, String());