diff --git a/text-minimessage/src/main/java/net/kyori/adventure/text/minimessage/tag/resolver/TagResolverBuilderImpl.java b/text-minimessage/src/main/java/net/kyori/adventure/text/minimessage/tag/resolver/TagResolverBuilderImpl.java
index 325c9ac45..edaf3356b 100644
--- a/text-minimessage/src/main/java/net/kyori/adventure/text/minimessage/tag/resolver/TagResolverBuilderImpl.java
+++ b/text-minimessage/src/main/java/net/kyori/adventure/text/minimessage/tag/resolver/TagResolverBuilderImpl.java
@@ -30,6 +30,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.stream.Collector;
+import net.kyori.adventure.text.minimessage.internal.TagInternals;
 import net.kyori.adventure.text.minimessage.tag.Tag;
 import org.jetbrains.annotations.NotNull;
 
@@ -48,8 +49,9 @@ final class TagResolverBuilderImpl implements TagResolver.Builder {
 
   @Override
   public TagResolver.@NotNull Builder tag(final @NotNull String name, final @NotNull Tag tag) {
+    TagInternals.assertValidTagName(requireNonNull(name, "name"));
     this.replacements.put(
-      requireNonNull(name, "name"),
+      name,
       requireNonNull(tag, "tag")
     );
     return this;
diff --git a/text-minimessage/src/test/java/net/kyori/adventure/text/minimessage/tag/TagResolverTest.java b/text-minimessage/src/test/java/net/kyori/adventure/text/minimessage/tag/TagResolverTest.java
index c3238b5a4..10ab0c79a 100644
--- a/text-minimessage/src/test/java/net/kyori/adventure/text/minimessage/tag/TagResolverTest.java
+++ b/text-minimessage/src/test/java/net/kyori/adventure/text/minimessage/tag/TagResolverTest.java
@@ -128,6 +128,12 @@ void testInvalidTagName() {
     assertThrows(IllegalArgumentException.class, () -> TagResolver.resolver("#test#", Tag.preProcessParsed("something")));
   }
 
+  // https://github.com/KyoriPowered/adventure/issues/763
+  @Test
+  void testBuilderValidatesTagName() {
+    assertThrows(IllegalArgumentException.class, () -> TagResolver.builder().tag("INVALID#NAME", Tag.preProcessParsed("something")));
+  }
+
   @Test
   void testValidTagName() {
     assertDoesNotThrow(() -> TagResolver.resolver("valid_-name0909", Tag.preProcessParsed("something")));