diff --git a/http-client/src/test/java/io/airlift/http/client/TestFullJsonResponseHandler.java b/http-client/src/test/java/io/airlift/http/client/TestFullJsonResponseHandler.java
index 252d8592f0..b781c86756 100644
--- a/http-client/src/test/java/io/airlift/http/client/TestFullJsonResponseHandler.java
+++ b/http-client/src/test/java/io/airlift/http/client/TestFullJsonResponseHandler.java
@@ -60,7 +60,7 @@ public void testInvalidJson()
         assertFalse(response.hasValue());
         assertEquals(response.getException().getMessage(), format("Unable to create %s from JSON response:\n[%s]", User.class, json));
         assertTrue(response.getException().getCause() instanceof IllegalArgumentException);
-        assertEquals(response.getException().getCause().getMessage(), "Invalid json bytes for [simple type, class io.airlift.http.client.TestFullJsonResponseHandler$User]");
+        assertEquals(response.getException().getCause().getMessage(), "Invalid JSON bytes for [simple type, class io.airlift.http.client.TestFullJsonResponseHandler$User]");
 
         assertEquals(response.getJsonBytes(), json.getBytes(UTF_8));
         assertEquals(response.getJson(), json);
diff --git a/http-client/src/test/java/io/airlift/http/client/TestJsonResponseHandler.java b/http-client/src/test/java/io/airlift/http/client/TestJsonResponseHandler.java
index 0b00e7b35c..cef28705ce 100644
--- a/http-client/src/test/java/io/airlift/http/client/TestJsonResponseHandler.java
+++ b/http-client/src/test/java/io/airlift/http/client/TestJsonResponseHandler.java
@@ -42,7 +42,7 @@ public void testInvalidJson()
         catch (IllegalArgumentException e) {
             assertEquals(e.getMessage(), format("Unable to create %s from JSON response:\n[%s]", User.class, json));
             assertTrue(e.getCause() instanceof IllegalArgumentException);
-            assertEquals(e.getCause().getMessage(), "Invalid json bytes for [simple type, class io.airlift.http.client.TestFullJsonResponseHandler$User]");
+            assertEquals(e.getCause().getMessage(), "Invalid JSON bytes for [simple type, class io.airlift.http.client.TestFullJsonResponseHandler$User]");
         }
     }
 
diff --git a/json/src/main/java/io/airlift/json/JsonCodec.java b/json/src/main/java/io/airlift/json/JsonCodec.java
index 274b3005e4..fa262b859e 100644
--- a/json/src/main/java/io/airlift/json/JsonCodec.java
+++ b/json/src/main/java/io/airlift/json/JsonCodec.java
@@ -32,6 +32,7 @@
 
 import static com.fasterxml.jackson.databind.SerializationFeature.INDENT_OUTPUT;
 import static com.google.common.base.Preconditions.checkNotNull;
+import static java.lang.String.format;
 
 public class JsonCodec<T>
 {
@@ -138,7 +139,7 @@ public T fromJson(String json)
             return mapper.readValue(json, javaType);
         }
         catch (IOException e) {
-            throw new IllegalArgumentException(String.format("Invalid json string for %s", javaType), e);
+            throw new IllegalArgumentException(format("Invalid JSON string for %s", javaType), e);
         }
     }
 
@@ -156,7 +157,7 @@ public String toJson(T instance)
             return mapper.writeValueAsString(instance);
         }
         catch (IOException e) {
-            throw new IllegalArgumentException(String.format("%s could not be converted to json", instance.getClass().getName()), e);
+            throw new IllegalArgumentException(format("%s could not be converted to JSON", instance.getClass().getName()), e);
         }
     }
 
@@ -179,7 +180,7 @@ public Optional<String> toJsonWithLengthLimit(T instance, int lengthLimit)
             return Optional.empty();
         }
         catch (IOException e) {
-            throw new IllegalArgumentException(String.format("%s could not be converted to json", instance.getClass().getName()), e);
+            throw new IllegalArgumentException(format("%s could not be converted to JSON", instance.getClass().getName()), e);
         }
     }
 
@@ -197,7 +198,7 @@ public T fromJson(byte[] json)
             return mapper.readValue(json, javaType);
         }
         catch (IOException e) {
-            throw new IllegalArgumentException(String.format("Invalid json bytes for %s", javaType), e);
+            throw new IllegalArgumentException(format("Invalid JSON bytes for %s", javaType), e);
         }
     }
 
@@ -215,7 +216,7 @@ public byte[] toJsonBytes(T instance)
             return mapper.writeValueAsBytes(instance);
         }
         catch (IOException e) {
-            throw new IllegalArgumentException(String.format("%s could not be converted to json", instance.getClass().getName()), e);
+            throw new IllegalArgumentException(format("%s could not be converted to JSON", instance.getClass().getName()), e);
         }
     }