diff --git a/build.gradle b/build.gradle
index a3956dc91..da3ef9882 100644
--- a/build.gradle
+++ b/build.gradle
@@ -291,7 +291,7 @@ project(':forge') {
         installer 'cpw.mods:modlauncher:0.11.+'
         installer 'net.minecraftforge:accesstransformers:0.15.+:shadowed'
         installer 'net.minecraftforge:eventbus:0.8.+:service'
-        installer 'net.minecraftforge:forgespi:0.8.+'
+        installer 'net.minecraftforge:forgespi:0.10.+'
         installer 'net.minecraftforge:coremods:0.4.+'
         installer 'net.minecraftforge:unsafe:0.2.+'
         installer 'com.electronwill.night-config:core:3.4.2'
diff --git a/src/fmllauncher/java/net/minecraftforge/fml/loading/moddiscovery/ModClassVisitor.java b/src/fmllauncher/java/net/minecraftforge/fml/loading/moddiscovery/ModClassVisitor.java
index c77934fdc..1c2705e39 100644
--- a/src/fmllauncher/java/net/minecraftforge/fml/loading/moddiscovery/ModClassVisitor.java
+++ b/src/fmllauncher/java/net/minecraftforge/fml/loading/moddiscovery/ModClassVisitor.java
@@ -75,7 +75,7 @@ public class ModClassVisitor extends ClassVisitor
         return new ModMethodVisitor(name, desc, annotations);
     }
 
-    public void buildData(final List<ModFileScanData.ClassData> classes, final List<ModFileScanData.AnnotationData> annotations) {
+    public void buildData(final Set<ModFileScanData.ClassData> classes, final Set<ModFileScanData.AnnotationData> annotations) {
         classes.add(new ModFileScanData.ClassData(this.asmType, this.asmSuperType, this.interfaces));
         final List<ModFileScanData.AnnotationData> collect = this.annotations.stream().
                 filter(ma->ModFileScanData.interestingAnnotations().test(ma.asmType)).
diff --git a/src/fmllauncher/java/net/minecraftforge/fml/loading/moddiscovery/ModFile.java b/src/fmllauncher/java/net/minecraftforge/fml/loading/moddiscovery/ModFile.java
index bd757cb71..2b4a2cee4 100644
--- a/src/fmllauncher/java/net/minecraftforge/fml/loading/moddiscovery/ModFile.java
+++ b/src/fmllauncher/java/net/minecraftforge/fml/loading/moddiscovery/ModFile.java
@@ -57,6 +57,7 @@ public class ModFile
     private final String jarVersion;
     private Map<String, Object> fileProperties;
     private IModLanguageProvider loader;
+    private Throwable scanError;
 
     public void setFileProperties(Map<String, Object> fileProperties)
     {
@@ -159,12 +160,18 @@ public class ModFile
                 e.printStackTrace();
             }
         }
+        if (this.scanError != null) {
+            throw new RuntimeException(this.scanError);
+        }
         return this.fileModFileScanData;
     }
 
     public void setScanResult(final ModFileScanData modFileScanData, final Throwable throwable) {
         this.futureScanResult = null;
         this.fileModFileScanData = modFileScanData;
+        if (throwable != null) {
+            this.scanError = throwable;
+        }
     }
 
     @Override
diff --git a/src/main/java/net/minecraftforge/fml/javafmlmod/FMLJavaModLanguageProvider.java b/src/main/java/net/minecraftforge/fml/javafmlmod/FMLJavaModLanguageProvider.java
index c5af734d5..f4f110ba5 100644
--- a/src/main/java/net/minecraftforge/fml/javafmlmod/FMLJavaModLanguageProvider.java
+++ b/src/main/java/net/minecraftforge/fml/javafmlmod/FMLJavaModLanguageProvider.java
@@ -95,7 +95,7 @@ public class FMLJavaModLanguageProvider implements IModLanguageProvider
                     .filter(ad -> ad.getAnnotationType().equals(MODANNOTATION))
                     .peek(ad -> LOGGER.debug(SCAN, "Found @Mod class {} with id {}", ad.getClassType().getClassName(), ad.getAnnotationData().get("value")))
                     .map(ad -> new FMLModTarget(ad.getClassType().getClassName(), (String)ad.getAnnotationData().get("value")))
-                    .collect(Collectors.toMap(FMLModTarget::getModId, Function.identity()));
+                    .collect(Collectors.toMap(FMLModTarget::getModId, Function.identity(), (a,b)->a));
             scanResult.addLanguageLoader(modTargetMap);
         };
     }