diff --git a/build.sbt b/build.sbt
index d0ade0876..65b5c0ad2 100644
--- a/build.sbt
+++ b/build.sbt
@@ -55,6 +55,7 @@ lazy val lmRoot = (project in file("."))
         },
         bintrayPackage := "librarymanagement",
         scalafmtOnCompile := true,
+        scalafmtOnCompile in Sbt := false,
         scalafmtVersion := "1.2.0",
         git.baseVersion := baseVersion,
         version := {
diff --git a/core/src/main/contraband-scala/sbt/librarymanagement/CrossVersion.scala b/core/src/main/contraband-scala/sbt/librarymanagement/CrossVersion.scala
index 321be7615..2c890a27b 100644
--- a/core/src/main/contraband-scala/sbt/librarymanagement/CrossVersion.scala
+++ b/core/src/main/contraband-scala/sbt/librarymanagement/CrossVersion.scala
@@ -11,7 +11,7 @@ abstract class CrossVersion() extends Serializable {
 
 
 override def equals(o: Any): Boolean = o match {
-  case x: CrossVersion => true
+  case _: CrossVersion => true
   case _ => false
 }
 override def hashCode: Int = {
diff --git a/core/src/main/contraband-scala/sbt/librarymanagement/Disabled.scala b/core/src/main/contraband-scala/sbt/librarymanagement/Disabled.scala
index 1c03d422e..6a3ccde72 100644
--- a/core/src/main/contraband-scala/sbt/librarymanagement/Disabled.scala
+++ b/core/src/main/contraband-scala/sbt/librarymanagement/Disabled.scala
@@ -10,7 +10,7 @@ final class Disabled private () extends sbt.librarymanagement.CrossVersion() wit
 
 
 override def equals(o: Any): Boolean = o match {
-  case x: Disabled => true
+  case _: Disabled => true
   case _ => false
 }
 override def hashCode: Int = {
diff --git a/core/src/main/contraband-scala/sbt/librarymanagement/Patch.scala b/core/src/main/contraband-scala/sbt/librarymanagement/Patch.scala
index ffdf666eb..65ec50436 100644
--- a/core/src/main/contraband-scala/sbt/librarymanagement/Patch.scala
+++ b/core/src/main/contraband-scala/sbt/librarymanagement/Patch.scala
@@ -13,7 +13,7 @@ final class Patch private () extends sbt.librarymanagement.CrossVersion() with S
 
 
 override def equals(o: Any): Boolean = o match {
-  case x: Patch => true
+  case _: Patch => true
   case _ => false
 }
 override def hashCode: Int = {
diff --git a/core/src/main/contraband-scala/sbt/librarymanagement/SshAuthentication.scala b/core/src/main/contraband-scala/sbt/librarymanagement/SshAuthentication.scala
index af49207c4..2ad8a3f57 100644
--- a/core/src/main/contraband-scala/sbt/librarymanagement/SshAuthentication.scala
+++ b/core/src/main/contraband-scala/sbt/librarymanagement/SshAuthentication.scala
@@ -10,7 +10,7 @@ abstract class SshAuthentication() extends Serializable {
 
 
 override def equals(o: Any): Boolean = o match {
-  case x: SshAuthentication => true
+  case _: SshAuthentication => true
   case _ => false
 }
 override def hashCode: Int = {
diff --git a/core/src/main/scala/sbt/librarymanagement/RichUpdateReport.scala b/core/src/main/scala/sbt/librarymanagement/RichUpdateReport.scala
index 297611b64..d8e5ca795 100644
--- a/core/src/main/scala/sbt/librarymanagement/RichUpdateReport.scala
+++ b/core/src/main/scala/sbt/librarymanagement/RichUpdateReport.scala
@@ -2,6 +2,8 @@ package sbt
 package librarymanagement
 
 import java.io.File
+import java.io.FileNotFoundException
+import sbt.io.IO
 
 /**
  * Provides extra methods for filtering the contents of an `UpdateReport`
@@ -10,7 +12,18 @@ import java.io.File
 final class RichUpdateReport(report: UpdateReport) {
   private[sbt] def recomputeStamps(): UpdateReport = {
     val files = report.cachedDescriptor +: allFiles
-    val stamps = files.map(f => (f, f.lastModified)).toMap
+    val stamps = files
+      .map(
+        f =>
+          (f,
+           // TODO: this used to be a lastModified(), without error checking.
+           // On occasion, "files" contains files like "./target/ivyhome/resolution-cache/com.example/foo/0.4.0/resolved.xml.xml",
+           // which do not actually exist, so getModifiedTime() correctly throws an exception. For the moment, the behavior of
+           // lastModified() is reproduced, but the non-existent file should really not be there to begin with. so, FIXME.
+           try IO.getModifiedTime(f)
+           catch { case _: FileNotFoundException => 0L })
+      )
+      .toMap
     UpdateReport(report.cachedDescriptor, report.configurations, report.stats, stamps)
   }
 
diff --git a/ivy/src/main/scala/sbt/internal/librarymanagement/ivyint/GigahorseUrlHandler.scala b/ivy/src/main/scala/sbt/internal/librarymanagement/ivyint/GigahorseUrlHandler.scala
index a1109dc91..32bbaf516 100644
--- a/ivy/src/main/scala/sbt/internal/librarymanagement/ivyint/GigahorseUrlHandler.scala
+++ b/ivy/src/main/scala/sbt/internal/librarymanagement/ivyint/GigahorseUrlHandler.scala
@@ -149,7 +149,7 @@ class GigahorseUrlHandler extends AbstractURLHandler {
 
       val lastModified = lastModifiedTimestamp(response)
       if (lastModified > 0) {
-        dest.setLastModified(lastModified)
+        IO.setModifiedTime(dest, lastModified)
       }
 
       if (l != null) {
diff --git a/project/Dependencies.scala b/project/Dependencies.scala
index 6a7a0f7b6..1a71abf72 100644
--- a/project/Dependencies.scala
+++ b/project/Dependencies.scala
@@ -6,8 +6,8 @@ object Dependencies {
   val scala211 = "2.11.12"
   val scala212 = "2.12.4"
 
-  private val ioVersion = "1.0.2"
-  private val utilVersion = "1.0.3"
+  private val ioVersion = "1.1.2"
+  private val utilVersion = "1.1.1"
 
   private val sbtIO = "org.scala-sbt" %% "io" % ioVersion
 
diff --git a/project/Util.scala b/project/Util.scala
index 5dacc7df8..2ef855762 100644
--- a/project/Util.scala
+++ b/project/Util.scala
@@ -26,6 +26,8 @@ object Util {
     val timestamp = formatter.format(new Date)
     val content = versionLine(version) + "\ntimestamp=" + timestamp
     val f = dir / "xsbt.version.properties"
+    // TODO: replace lastModified() with sbt.io.Milli.getModifiedTime(), once the build
+    // has been upgraded to a version of sbt that includes sbt.io.Milli.
     if (!f.exists || f.lastModified < lastCompilationTime(analysis) || !containsVersion(f, version)) {
       s.log.info("Writing version information to " + f + " :\n" + content)
       IO.write(f, content)
diff --git a/project/plugins.sbt b/project/plugins.sbt
index f82b39957..7a0426d32 100644
--- a/project/plugins.sbt
+++ b/project/plugins.sbt
@@ -1,6 +1,4 @@
-addSbtPlugin("org.scala-sbt" % "sbt-houserules" % "0.3.3")
-addSbtPlugin("org.scala-sbt" % "sbt-contraband" % "0.3.0")
-addSbtPlugin("com.lucidchart" % "sbt-scalafmt" % "1.10")
-addSbtPlugin("com.typesafe" % "sbt-mima-plugin" % "0.1.17")
+addSbtPlugin("org.scala-sbt" % "sbt-houserules" % "0.3.4")
+addSbtPlugin("org.scala-sbt" % "sbt-contraband" % "0.3.2")
 
 scalacOptions += "-language:postfixOps"