diff --git a/src/json.hpp b/src/json.hpp
index 5190c64e9..879d8be57 100644
--- a/src/json.hpp
+++ b/src/json.hpp
@@ -3978,7 +3978,7 @@ class basic_json
                     {
                         // control characters (everything between 0x00 and 0x1f)
                         // -> create four-digit hex representation
-                        o << "\\u" << std::hex << std::setw(4) << std::setfill('0') << int(c);
+                        o << "\\u" << std::hex << std::setw(4) << std::setfill('0') << int(c) << std::dec;
                     }
                     else
                     {
diff --git a/src/json.hpp.re2c b/src/json.hpp.re2c
index 3650c8e73..5a9d4ab33 100644
--- a/src/json.hpp.re2c
+++ b/src/json.hpp.re2c
@@ -3978,7 +3978,7 @@ class basic_json
                     {
                         // control characters (everything between 0x00 and 0x1f)
                         // -> create four-digit hex representation
-                        o << "\\u" << std::hex << std::setw(4) << std::setfill('0') << int(c);
+                        o << "\\u" << std::hex << std::setw(4) << std::setfill('0') << int(c) << std::dec;
                     }
                     else
                     {
diff --git a/test/unit.cpp b/test/unit.cpp
index 64e67752d..935c665fe 100644
--- a/test/unit.cpp
+++ b/test/unit.cpp
@@ -9276,4 +9276,16 @@ TEST_CASE("regression tests")
         // we need to cast to int to compile with Catch - the value is int32_t
         CHECK(static_cast<int>(j["int_1"]) == 1);
     }
+
+    SECTION("issue #101 - binary string causes numbers to be dumped as hex")
+    {
+        int64_t number = 10;
+        std::string bytes{"\x00" "asdf\n", 6};
+        json j;
+        j["int64"] = number;
+        j["binary string"] = bytes;
+        // make sure the number is really printed as decimal "10" and not as
+        // hexadecimal "a"
+        CHECK(j.dump() == "{\"binary string\":\"\\u0000asdf\\n\",\"int64\":10}");
+    }
 }