diff --git a/wire-java-generator/src/test/java/com/squareup/wire/java/JavaGeneratorTest.java b/wire-java-generator/src/test/java/com/squareup/wire/java/JavaGeneratorTest.java
index 40191e77ca..8f5033a559 100644
--- a/wire-java-generator/src/test/java/com/squareup/wire/java/JavaGeneratorTest.java
+++ b/wire-java-generator/src/test/java/com/squareup/wire/java/JavaGeneratorTest.java
@@ -502,6 +502,8 @@ public void defaultValues() throws IOException {
                     + "  optional double f = 6 [default = -inf ];\n"
                     + "  optional double g = 7 [default = nan ];\n"
                     + "  optional double h = 8 [default = -nan ];\n"
+                    + "  optional int32 i = 9 [default = -0x80000000\n];\n"
+                    + "  optional int64 j = 10 [default = -0x7FFFFFFF\n];\n"
                     + "}\n")
             .build();
     String code = new JavaWithProfilesGenerator(schema).generateJava("Message");
@@ -513,6 +515,8 @@ public void defaultValues() throws IOException {
     assertThat(code).contains("  public static final Double DEFAULT_F = Double.NEGATIVE_INFINITY;");
     assertThat(code).contains("  public static final Double DEFAULT_G = Double.NaN;");
     assertThat(code).contains("  public static final Double DEFAULT_H = Double.NaN;");
+    assertThat(code).contains("  public static final Integer DEFAULT_I = -2147483648;");
+    assertThat(code).contains("  public static final Long DEFAULT_J = -2147483647L;");
   }
 
   @Test
diff --git a/wire-kotlin-generator/src/test/java/com/squareup/wire/kotlin/KotlinGeneratorTest.kt b/wire-kotlin-generator/src/test/java/com/squareup/wire/kotlin/KotlinGeneratorTest.kt
index 45a2426bde..f2a81da509 100644
--- a/wire-kotlin-generator/src/test/java/com/squareup/wire/kotlin/KotlinGeneratorTest.kt
+++ b/wire-kotlin-generator/src/test/java/com/squareup/wire/kotlin/KotlinGeneratorTest.kt
@@ -136,6 +136,8 @@ class KotlinGeneratorTest {
         |  optional double n = 14 [default = -inf];
         |  optional double o = 15 [default = nan];
         |  optional double p = 16 [default = -nan];
+        |  optional int32 q = 17 [default = -0x80000000];
+        |  optional int64 r = 18 [default = -0x7FFFFFFF];
         |}
         """.trimMargin(),
       )
@@ -160,6 +162,8 @@ class KotlinGeneratorTest {
     assertThat(code).contains("const val DEFAULT_N: Double = Double.NEGATIVE_INFINITY")
     assertThat(code).contains("const val DEFAULT_O: Double = Double.NaN")
     assertThat(code).contains("const val DEFAULT_P: Double = Double.NaN")
+    assertThat(code).contains("const val DEFAULT_Q: Int = Int.MIN_VALUE")
+    assertThat(code).contains("const val DEFAULT_R: Long = -2_147_483_647L")
   }
 
   @Test fun nameAllocatorIsUsed() {
diff --git a/wire-schema/src/jvmMain/kotlin/com/squareup/wire/schema/internal/JvmLanguages.kt b/wire-schema/src/jvmMain/kotlin/com/squareup/wire/schema/internal/JvmLanguages.kt
index 97ac5ad8b3..15fb43c0d8 100644
--- a/wire-schema/src/jvmMain/kotlin/com/squareup/wire/schema/internal/JvmLanguages.kt
+++ b/wire-schema/src/jvmMain/kotlin/com/squareup/wire/schema/internal/JvmLanguages.kt
@@ -119,10 +119,15 @@ fun optionValueToInt(value: Any?): Int {
   if (value == null) return 0
 
   val string = value.toString()
+  val negativeSign = if (string.startsWith('-')) { "-" } else { "" }
 
   return when {
     // Hexadecimal.
-    string.startsWith("0x") || string.startsWith("0X") -> string.substring("0x".length).toInt(16)
+    string.startsWith("${negativeSign}0x", ignoreCase = true) ->
+      buildString {
+        append(negativeSign)
+        append(string.substring("${negativeSign}0x".length))
+      }.toInt(16)
 
     // Octal.
     string.startsWith("0") && string != "0" -> error("Octal literal unsupported: $value")
@@ -136,10 +141,15 @@ fun optionValueToLong(value: Any?): Long {
   if (value == null) return 0L
 
   val string = value.toString()
+  val negativeSign = if (string.startsWith('-')) { "-" } else { "" }
 
   return when {
     // Hexadecimal.
-    string.startsWith("0x") || string.startsWith("0X") -> string.substring("0x".length).toLong(16)
+    string.startsWith("${negativeSign}0x", ignoreCase = true) ->
+      buildString {
+        append(negativeSign)
+        append(string.substring("${negativeSign}0x".length))
+      }.toLong(16)
 
     // Octal.
     string.startsWith("0") && string != "0" -> error("Octal literal unsupported: $value")