diff --git a/changelog/@unreleased/pr-1715.v2.yml b/changelog/@unreleased/pr-1715.v2.yml
new file mode 100644
index 000000000..8bcf6e1f7
--- /dev/null
+++ b/changelog/@unreleased/pr-1715.v2.yml
@@ -0,0 +1,5 @@
+type: improvement
+improvement:
+  description: Avoid recomputing valid regexes String in FieldNameValidator.validate()
+  links:
+  - https://github.com/palantir/conjure/pull/1715
diff --git a/conjure-core/src/main/java/com/palantir/conjure/defs/validator/FieldNameValidator.java b/conjure-core/src/main/java/com/palantir/conjure/defs/validator/FieldNameValidator.java
index 822b9403f..de164ec68 100644
--- a/conjure-core/src/main/java/com/palantir/conjure/defs/validator/FieldNameValidator.java
+++ b/conjure-core/src/main/java/com/palantir/conjure/defs/validator/FieldNameValidator.java
@@ -16,8 +16,8 @@
 
 package com.palantir.conjure.defs.validator;
 
-import com.google.common.base.Preconditions;
 import com.palantir.conjure.CaseConverter;
+import com.palantir.conjure.CaseConverter.Case;
 import com.palantir.conjure.spec.FieldName;
 import java.util.Arrays;
 import org.apache.commons.lang3.StringUtils;
@@ -47,13 +47,14 @@ public static FieldName toCase(FieldName fieldName, CaseConverter.Case targetCas
     public static void validate(FieldName fieldName) {
         boolean matchesCamelCase = CaseConverter.CAMEL_CASE_PATTERN.matches(fieldName.get());
 
-        Preconditions.checkArgument(
-                matchesCamelCase
-                        || CaseConverter.KEBAB_CASE_PATTERN.matches(fieldName.get())
-                        || CaseConverter.SNAKE_CASE_PATTERN.matches(fieldName.get()),
-                "FieldName \"%s\" must follow one of the following patterns: %s",
-                fieldName,
-                Arrays.toString(CaseConverter.Case.values()));
+        if (!matchesCamelCase
+                && !CaseConverter.KEBAB_CASE_PATTERN.matches(fieldName.get())
+                && !CaseConverter.SNAKE_CASE_PATTERN.matches(fieldName.get())) {
+            // using if-throw instead of Preconditions to avoid recomputing the `Arrays.toString()` every time
+            throw new IllegalArgumentException(String.format(
+                    "FieldName \"%s\" must follow one of the following patterns: %s",
+                    fieldName, Arrays.toString(Case.values())));
+        }
 
         if (!matchesCamelCase) {
             log.warn(
diff --git a/conjure-core/src/test/java/com/palantir/conjure/defs/validator/FieldNameValidatorTest.java b/conjure-core/src/test/java/com/palantir/conjure/defs/validator/FieldNameValidatorTest.java
index 0b8aa1fe6..ce77fb534 100644
--- a/conjure-core/src/test/java/com/palantir/conjure/defs/validator/FieldNameValidatorTest.java
+++ b/conjure-core/src/test/java/com/palantir/conjure/defs/validator/FieldNameValidatorTest.java
@@ -40,7 +40,7 @@ public void testValidNames() {
     }
 
     @Test
-    public void testInvalidNames() throws Exception {
+    public void testInvalidNames() {
         for (String invalid : new String[] {
             "UpperCamelCase",
             "Upper-Kebab-Case",
@@ -55,18 +55,20 @@ public void testInvalidNames() throws Exception {
         }) {
             assertThatThrownBy(() -> FieldNameValidator.validate(FieldName.of(invalid)))
                     .isInstanceOf(IllegalArgumentException.class)
-                    .hasMessageContaining(
-                            String.format("FieldName \"%s\" must follow one of the following patterns", invalid));
+                    .hasMessageContainingAll(
+                            String.format("FieldName \"%s\" must follow one of the following patterns: ", invalid),
+                            "LOWER_CAMEL_CASE",
+                            "[A-Z]");
         }
     }
 
     @Test
-    public void capitalize_should_turn_camel_case_into_sensible_class_name() throws Exception {
+    public void capitalize_should_turn_camel_case_into_sensible_class_name() {
         assertThat(FieldNameValidator.capitalize(FieldName.of("myVariant"))).isEqualTo("MyVariant");
     }
 
     @Test
-    public void capitalize_capture_unused_behavior() throws Exception {
+    public void capitalize_capture_unused_behavior() {
         assertThat(FieldNameValidator.capitalize(FieldName.of("my-variant"))).isEqualTo("My-variant");
         assertThat(FieldNameValidator.capitalize(FieldName.of("my_variant"))).isEqualTo("My_variant");
     }