diff --git a/enigma-cli/src/main/java/cuchaz/enigma/command/CheckMappingsCommand.java b/enigma-cli/src/main/java/cuchaz/enigma/command/CheckMappingsCommand.java
index 75ef225ae..3d20b2b5a 100644
--- a/enigma-cli/src/main/java/cuchaz/enigma/command/CheckMappingsCommand.java
+++ b/enigma-cli/src/main/java/cuchaz/enigma/command/CheckMappingsCommand.java
@@ -3,17 +3,21 @@
 import cuchaz.enigma.Enigma;
 import cuchaz.enigma.EnigmaProject;
 import cuchaz.enigma.ProgressListener;
-import cuchaz.enigma.analysis.index.JarIndex;
 import cuchaz.enigma.classprovider.ClasspathClassProvider;
+import cuchaz.enigma.command.checks.CheckFailureException;
+import cuchaz.enigma.command.checks.CheckInvalidMappings;
+import cuchaz.enigma.command.checks.CheckNamedSyntheticEntry;
+import cuchaz.enigma.command.checks.MappingCheck;
+import cuchaz.enigma.command.checks.CheckPackageVisibility;
 import cuchaz.enigma.translation.mapping.EntryMapping;
 import cuchaz.enigma.translation.mapping.serde.MappingSaveParameters;
 import cuchaz.enigma.translation.mapping.serde.MappingFormat;
 import cuchaz.enigma.translation.mapping.tree.EntryTree;
-import cuchaz.enigma.translation.representation.entry.ClassEntry;
 
 import java.nio.file.Path;
+import java.util.HashSet;
+import java.util.LinkedList;
 import java.util.Set;
-import java.util.stream.Collectors;
 
 public class CheckMappingsCommand extends Command {
 
@@ -50,29 +54,30 @@ public void run(String... args) throws Exception {
 		EntryTree<EntryMapping> mappings = format.read(fileMappings, ProgressListener.none(), saveParameters);
 		project.setMappings(mappings);
 
-		JarIndex idx = project.getJarIndex();
-
-		boolean error = false;
-
-		for (Set<ClassEntry> partition : idx.getPackageVisibilityIndex().getPartitions()) {
-			long packages = partition.stream()
-					.map(project.getMapper()::deobfuscate)
-					.map(ClassEntry::getPackageName)
-					.distinct()
-					.count();
-			if (packages > 1) {
-				error = true;
-				System.err.println("ERROR: Must be in one package:\n" + partition.stream()
-						.map(project.getMapper()::deobfuscate)
-						.map(ClassEntry::toString)
-						.sorted()
-						.collect(Collectors.joining("\n"))
-				);
-			}
+		Set<MappingCheck> checks = new HashSet<>();
+		checks.add(new CheckPackageVisibility());
+		checks.add(new CheckInvalidMappings());
+		checks.add(new CheckNamedSyntheticEntry());
+
+		LinkedList<CheckFailureException> errors = new LinkedList<>();
+		LinkedList<CheckFailureException> warnings = new LinkedList<>();
+
+		for (MappingCheck check : checks) {
+			check.findErrors(project, check.failOnError() ? errors : warnings);
 		}
 
-		if (error) {
-			throw new IllegalStateException("Errors in package visibility detected, see SysErr above");
+		System.out.printf("%d warnings:\n", warnings.size());
+		for (CheckFailureException warning : warnings) {
+			System.out.println(warning.getMessage());
+		}
+
+		System.out.printf("%d errors:\n", errors.size());
+		if (!errors.isEmpty()) {
+			for (CheckFailureException error : errors) {
+				System.err.println(error.getMessage());
+			}
+
+			throw new IllegalStateException("Mappings check failed, see above output");
 		}
 	}
 }
diff --git a/enigma-cli/src/main/java/cuchaz/enigma/command/checks/CheckFailureException.java b/enigma-cli/src/main/java/cuchaz/enigma/command/checks/CheckFailureException.java
new file mode 100644
index 000000000..b07ec05cf
--- /dev/null
+++ b/enigma-cli/src/main/java/cuchaz/enigma/command/checks/CheckFailureException.java
@@ -0,0 +1,7 @@
+package cuchaz.enigma.command.checks;
+
+public class CheckFailureException extends RuntimeException {
+	public CheckFailureException(String message) {
+		super(message);
+	}
+}
diff --git a/enigma-cli/src/main/java/cuchaz/enigma/command/checks/CheckInvalidMappings.java b/enigma-cli/src/main/java/cuchaz/enigma/command/checks/CheckInvalidMappings.java
new file mode 100644
index 000000000..5be90aa2b
--- /dev/null
+++ b/enigma-cli/src/main/java/cuchaz/enigma/command/checks/CheckInvalidMappings.java
@@ -0,0 +1,18 @@
+package cuchaz.enigma.command.checks;
+
+import cuchaz.enigma.EnigmaProject;
+import cuchaz.enigma.ProgressListener;
+import cuchaz.enigma.translation.representation.entry.Entry;
+
+import java.util.Collection;
+
+public class CheckInvalidMappings implements MappingCheck {
+	@Override
+	public void findErrors(EnigmaProject project, Collection<CheckFailureException> errors) {
+		Collection<Entry<?>> invalidEntries = project.dropMappings(ProgressListener.none());
+
+		for (Entry<?> invalidEntry : invalidEntries) {
+			errors.add(new CheckFailureException("Found invalid mapping entry: " + invalidEntry.toString()));
+		}
+	}
+}
diff --git a/enigma-cli/src/main/java/cuchaz/enigma/command/checks/CheckNamedSyntheticEntry.java b/enigma-cli/src/main/java/cuchaz/enigma/command/checks/CheckNamedSyntheticEntry.java
new file mode 100644
index 000000000..70be8d9e5
--- /dev/null
+++ b/enigma-cli/src/main/java/cuchaz/enigma/command/checks/CheckNamedSyntheticEntry.java
@@ -0,0 +1,28 @@
+package cuchaz.enigma.command.checks;
+
+import cuchaz.enigma.EnigmaProject;
+import cuchaz.enigma.analysis.index.EntryIndex;
+import cuchaz.enigma.translation.representation.entry.DefEntry;
+import cuchaz.enigma.translation.representation.entry.Entry;
+
+import java.util.Collection;
+
+public class CheckNamedSyntheticEntry implements MappingCheck {
+	@Override
+	public void findErrors(EnigmaProject project, Collection<CheckFailureException> errors) {
+		EntryIndex entryIndex = project.getJarIndex().getEntryIndex();
+
+		check(entryIndex.getClasses(), project, errors);
+		check(entryIndex.getMethods(), project, errors);
+		check(entryIndex.getFields(), project, errors);
+	}
+
+	private void check(Collection<? extends Entry<?>> entries, EnigmaProject project, Collection<CheckFailureException> errors) {
+		for (Entry<?> entry : entries) {
+			DefEntry<?> defEntry = (DefEntry<?>) entry;
+			if (defEntry.getAccess().isSynthetic() && project.getMapper().hasDeobfMapping(entry)) {
+				errors.add(new CheckFailureException(String.format("Synthetic entry (%s) has a debof name (%s)", entry, project.getMapper().getDeobfMapping(entry).getTargetName())));
+			}
+		}
+	}
+}
diff --git a/enigma-cli/src/main/java/cuchaz/enigma/command/checks/CheckPackageVisibility.java b/enigma-cli/src/main/java/cuchaz/enigma/command/checks/CheckPackageVisibility.java
new file mode 100644
index 000000000..ff6df3059
--- /dev/null
+++ b/enigma-cli/src/main/java/cuchaz/enigma/command/checks/CheckPackageVisibility.java
@@ -0,0 +1,38 @@
+package cuchaz.enigma.command.checks;
+
+import cuchaz.enigma.EnigmaProject;
+import cuchaz.enigma.analysis.index.JarIndex;
+import cuchaz.enigma.translation.representation.entry.ClassEntry;
+
+import java.util.Collection;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+public class CheckPackageVisibility implements MappingCheck {
+	@Override
+	public void findErrors(EnigmaProject project, Collection<CheckFailureException> errors) {
+		JarIndex idx = project.getJarIndex();
+
+		for (Set<ClassEntry> partition : idx.getPackageVisibilityIndex().getPartitions()) {
+			long packages = partition.stream()
+					.map(project.getMapper()::deobfuscate)
+					.map(ClassEntry::getPackageName)
+					.distinct()
+					.count();
+
+			if (packages > 1) {
+				errors.add(new CheckFailureException("ERROR: Must be in one package:\n" + partition.stream()
+						.map(project.getMapper()::deobfuscate)
+						.map(ClassEntry::toString)
+						.sorted()
+						.collect(Collectors.joining("\n"))
+				));
+			}
+		}
+	}
+
+	@Override
+	public boolean failOnError() {
+		return false;
+	}
+}
diff --git a/enigma-cli/src/main/java/cuchaz/enigma/command/checks/MappingCheck.java b/enigma-cli/src/main/java/cuchaz/enigma/command/checks/MappingCheck.java
new file mode 100644
index 000000000..fbdee8dbe
--- /dev/null
+++ b/enigma-cli/src/main/java/cuchaz/enigma/command/checks/MappingCheck.java
@@ -0,0 +1,13 @@
+package cuchaz.enigma.command.checks;
+
+import cuchaz.enigma.EnigmaProject;
+
+import java.util.Collection;
+
+public interface MappingCheck {
+	void findErrors(EnigmaProject project, Collection<CheckFailureException> errors);
+
+	default boolean failOnError() {
+		return true;
+	}
+}
diff --git a/enigma/src/main/java/cuchaz/enigma/EnigmaProject.java b/enigma/src/main/java/cuchaz/enigma/EnigmaProject.java
index a01eca194..49051d681 100644
--- a/enigma/src/main/java/cuchaz/enigma/EnigmaProject.java
+++ b/enigma/src/main/java/cuchaz/enigma/EnigmaProject.java
@@ -97,13 +97,15 @@ public EntryRemapper getMapper() {
 		return mapper;
 	}
 
-	public void dropMappings(ProgressListener progress) {
+	public Collection<Entry<?>> dropMappings(ProgressListener progress) {
 		DeltaTrackingTree<EntryMapping> mappings = mapper.getObfToDeobf();
 
 		Collection<Entry<?>> dropped = dropMappings(mappings, progress);
 		for (Entry<?> entry : dropped) {
 			mappings.trackChange(entry);
 		}
+
+		return dropped;
 	}
 
 	private Collection<Entry<?>> dropMappings(EntryTree<EntryMapping> mappings, ProgressListener progress) {