diff --git a/compile/interface/API.scala b/compile/interface/API.scala
index 9985f4c67..35e441fbe 100644
--- a/compile/interface/API.scala
+++ b/compile/interface/API.scala
@@ -44,14 +44,29 @@ final class API(val global: Global, val callback: xsbti.AnalysisCallback) extend
 			val packages = traverser.packages.toArray[String].map(p => new xsbti.api.Package(p))
 			val source = new xsbti.api.Source(packages, traverser.definitions.toArray[xsbti.api.Definition])
 			forceStructures()
+			clearCaches()
 			callback.api(sourceFile, source)
 		}
 	}
 
+	// this cache reduces duplicate work both here and when persisting
+	//   caches on other structures had minimal effect on time and cache size
+	//   (tried: Definition, Modifier, Path, Id, String)
+	private[this] val typeCache = new HashMap[Type, xsbti.api.Type]
+	// these caches are necessary for correctness
 	private[this] val structureCache = new HashMap[Symbol, xsbti.api.Structure]
 	private[this] val classLikeCache = new HashMap[Symbol, xsbti.api.ClassLike]
 	private[this] val pending = new HashSet[xsbti.api.Lazy[_]]
 
+	// to mitigate "temporary leaks" like that caused by NoPhase in 2.8.0,
+	//   this ensures this class is not retaining objects
+	private def clearCaches()
+	{
+		typeCache.clear()
+		structureCache.clear()
+		classLikeCache.clear()
+	}
+
 	// call back to the xsbti.SafeLazy class in main sbt code to construct a SafeLazy instance
 	//   we pass a thunk, whose class is loaded by the interface class loader (this class's loader)
 	//   SafeLazy ensures that once the value is forced, the thunk is nulled out and so 
@@ -256,6 +271,7 @@ final class API(val global: Global, val callback: xsbti.AnalysisCallback) extend
 		new xsbti.api.Modifiers(s.hasFlag(ABSTRACT) || s.hasFlag(DEFERRED), s.hasFlag(OVERRIDE),
 			s.isFinal, s.hasFlag(SEALED), isImplicit(s), s.hasFlag(LAZY))
 	}
+
 	private def isImplicit(s: Symbol) = s.hasFlag(Flags.IMPLICIT)
 	private def getAccess(c: Symbol): xsbti.api.Access =
 	{
@@ -270,7 +286,8 @@ final class API(val global: Global, val callback: xsbti.AnalysisCallback) extend
 			else new xsbti.api.Private(qualifier)
 		}
 	}
-	private def processType(t: Type): xsbti.api.Type =
+	private def processType(t: Type): xsbti.api.Type = typeCache.getOrElseUpdate(t, makeType(t))
+	private def makeType(t: Type): xsbti.api.Type =
 	{
 		def dealias(t: Type) = t match { case TypeRef(_, sym, _) if sym.isAliasType => t.normalize; case _ => t }
 
@@ -394,5 +411,5 @@ final class API(val global: Global, val callback: xsbti.AnalysisCallback) extend
 		if(annots.isEmpty) processType(at.underlying) else annotated(annots, at.underlying)
 	}
 	private def fullName(s: Symbol): String = nameString(s)
-	private def simpleName(s: Symbol): String = s.simpleName.toString.trim	
+	private def simpleName(s: Symbol): String = s.simpleName.toString.trim
 }
diff --git a/interface/other b/interface/other
index bba27dc7f..2ee086bcb 100644
--- a/interface/other
+++ b/interface/other
@@ -18,14 +18,6 @@ Qualifier
 	IdQualifier
 		value: String
 
-Modifiers
-	isAbstract: Boolean
-	isOverride: Boolean
-	isFinal: Boolean
-	isSealed: Boolean
-	isImplicit: Boolean
-	isLazy: Boolean
-
 ParameterList
 	parameters: MethodParameter*
 	isImplicit: Boolean
diff --git a/interface/src/main/java/xsbti/api/Modifiers.java b/interface/src/main/java/xsbti/api/Modifiers.java
new file mode 100644
index 000000000..14737be57
--- /dev/null
+++ b/interface/src/main/java/xsbti/api/Modifiers.java
@@ -0,0 +1,69 @@
+package xsbti.api;
+
+public final class Modifiers implements java.io.Serializable
+{
+	private static final int AbstractBit = 0;
+	private static final int OverrideBit = 1;
+	private static final int FinalBit = 2;
+	private static final int SealedBit = 3;
+	private static final int ImplicitBit = 4;
+	private static final int LazyBit = 5;
+
+	private static final int flag(boolean set, int bit)
+	{
+		return set ? (1 << bit) : 0;
+	}
+
+	public Modifiers(boolean isAbstract, boolean isOverride, boolean isFinal, boolean isSealed, boolean isImplicit, boolean isLazy)
+	{
+		this.flags = (byte)(
+			flag(isAbstract, AbstractBit) |
+			flag(isOverride, OverrideBit) |
+			flag(isFinal, FinalBit) |
+			flag(isSealed, SealedBit) |
+			flag(isImplicit, ImplicitBit) |
+			flag(isLazy, LazyBit)
+		);
+	}
+
+	private final byte flags;
+
+	private final boolean flag(int bit)
+	{
+		return (flags & (1 << bit)) != 0;
+	}
+
+	public final byte raw()
+	{
+		return flags;
+	}
+
+	public final boolean isAbstract()
+	{
+		return flag(AbstractBit);
+	}
+	public final boolean isOverride()
+	{
+		return flag(OverrideBit);
+	}
+	public final boolean isFinal()
+	{
+		return flag(FinalBit);
+	}
+	public final boolean isSealed()
+	{
+		return flag(SealedBit);
+	}
+	public final boolean isImplicit()
+	{
+		return flag(ImplicitBit);
+	}
+	public final boolean isLazy()
+	{
+		return flag(LazyBit);
+	}
+	public String toString()
+	{
+		return "Modifiers(" + "isAbstract: " + isAbstract() + ", " + "isOverride: " + isOverride() + ", " + "isFinal: " + isFinal() + ", " + "isSealed: " + isSealed() + ", " + "isImplicit: " + isImplicit() + ", " + "isLazy: " + isLazy()+ ")";
+	}
+}