diff --git a/Makefile b/Makefile
index 21e436c45..dfaf6406e 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,7 @@
 export GOBIN ?= $(shell pwd)/bin
 
 GOLINT = $(GOBIN)/golint
+STATICCHECK = $(GOBIN)/staticcheck
 BENCH_FLAGS ?= -cpuprofile=cpu.pprof -memprofile=mem.pprof -benchmem
 
 # Directories containing independent Go modules.
@@ -17,7 +18,7 @@ GO_FILES := $(shell \
 all: lint test
 
 .PHONY: lint
-lint: $(GOLINT)
+lint: $(GOLINT) $(STATICCHECK)
 	@rm -rf lint.log
 	@echo "Checking formatting..."
 	@gofmt -d -s $(GO_FILES) 2>&1 | tee lint.log
@@ -25,6 +26,8 @@ lint: $(GOLINT)
 	@$(foreach dir,$(MODULE_DIRS),(cd $(dir) && go vet ./... 2>&1) &&) true | tee -a lint.log
 	@echo "Checking lint..."
 	@$(foreach dir,$(MODULE_DIRS),(cd $(dir) && $(GOLINT) ./... 2>&1) &&) true | tee -a lint.log
+	@echo "Checking staticcheck..."
+	@$(foreach dir,$(MODULE_DIRS),(cd $(dir) && $(STATICCHECK) ./... 2>&1) &&) true | tee -a lint.log
 	@echo "Checking for unresolved FIXMEs..."
 	@git grep -i fixme | grep -v -e Makefile | tee -a lint.log
 	@echo "Checking for license headers..."
@@ -34,6 +37,9 @@ lint: $(GOLINT)
 $(GOLINT):
 	go install golang.org/x/lint/golint
 
+$(STATICCHECK):
+	go install honnef.co/go/tools/cmd/staticcheck
+
 .PHONY: test
 test:
 	@$(foreach dir,$(MODULE_DIRS),(cd $(dir) && go test -race ./...) &&) true
diff --git a/benchmarks/go.mod b/benchmarks/go.mod
index 04b8cebd0..3b3284409 100644
--- a/benchmarks/go.mod
+++ b/benchmarks/go.mod
@@ -10,7 +10,7 @@ require (
 	github.com/go-stack/stack v1.8.0 // indirect
 	github.com/rs/zerolog v1.16.0
 	github.com/sirupsen/logrus v1.4.2
-	go.uber.org/multierr v1.3.0
+	go.uber.org/multierr v1.5.0
 	go.uber.org/zap v0.0.0-00010101000000-000000000000
 	gopkg.in/inconshreveable/log15.v2 v2.0.0-20180818164646-67afb5ed74ec
 )
diff --git a/benchmarks/go.sum b/benchmarks/go.sum
index a88f4e059..251316f4d 100644
--- a/benchmarks/go.sum
+++ b/benchmarks/go.sum
@@ -69,12 +69,10 @@ github.com/tj/go-elastic v0.0.0-20171221160941-36157cbbebc2/go.mod h1:WjeM0Oo1eN
 github.com/tj/go-kinesis v0.0.0-20171128231115-08b17f58cb1b/go.mod h1:/yhzCV0xPfx6jb1bBgRFjl5lytqVqZXEaeqWP8lTEao=
 github.com/tj/go-spin v1.1.0/go.mod h1:Mg1mzmePZm4dva8Qz60H2lHwmJ2loum4VIrLgVnKwh4=
 github.com/zenazn/goji v0.9.0/go.mod h1:7S9M489iMyHBNxwZnk9/EHS098H4/F6TATF2mIxtB1Q=
-go.uber.org/atomic v1.5.0 h1:OI5t8sDa1Or+q8AeE+yKeB/SDYioSHAgcVljj9JIETY=
-go.uber.org/atomic v1.5.0/go.mod h1:sABNBOSYdrvTF6hTgEIbc7YasKWGhgEQZyfxyTvoXHQ=
-go.uber.org/multierr v1.2.0 h1:6I+W7f5VwC5SV9dNrZ3qXrDB9mD0dyGOi/ZJmYw03T4=
-go.uber.org/multierr v1.2.0/go.mod h1:wR5kodmAFQ0UK8QlbwjlSNy0Z68gJhDJUG5sjR94q/0=
-go.uber.org/multierr v1.3.0 h1:sFPn2GLc3poCkfrpIXGhBD2X0CMIo4Q/zSULXrj/+uc=
-go.uber.org/multierr v1.3.0/go.mod h1:VgVr7evmIr6uPjLBxg28wmKNXyqE9akIJ5XnfpiKl+4=
+go.uber.org/atomic v1.6.0 h1:Ezj3JGmsOnG1MoRWQkPBsKLe9DwWD9QeXzTRzzldNVk=
+go.uber.org/atomic v1.6.0/go.mod h1:sABNBOSYdrvTF6hTgEIbc7YasKWGhgEQZyfxyTvoXHQ=
+go.uber.org/multierr v1.5.0 h1:KCa4XfM8CWFCpxXRGok+Q0SS/0XBhMDbHHGABQLvD2A=
+go.uber.org/multierr v1.5.0/go.mod h1:FeouvMocqHpRaaGuG9EjoKcStLC43Zu/fmqdUMPcKYU=
 go.uber.org/tools v0.0.0-20190618225709-2cfd321de3ee h1:0mgffUl7nfd+FpvXMVz4IDEaUSmT1ysygQC7qYo7sG4=
 go.uber.org/tools v0.0.0-20190618225709-2cfd321de3ee/go.mod h1:vJERXedbb3MVM5f9Ejo0C68/HhF8uaILCdgjnY+goOA=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
diff --git a/go.mod b/go.mod
index 1fb6bba0b..118abda15 100644
--- a/go.mod
+++ b/go.mod
@@ -5,7 +5,8 @@ go 1.13
 require (
 	github.com/pkg/errors v0.8.1
 	github.com/stretchr/testify v1.4.0
-	go.uber.org/atomic v1.5.0
-	go.uber.org/multierr v1.3.0
+	go.uber.org/atomic v1.6.0
+	go.uber.org/multierr v1.5.0
 	golang.org/x/lint v0.0.0-20190930215403-16217165b5de
+	honnef.co/go/tools v0.0.1-2019.2.3
 )
diff --git a/go.sum b/go.sum
index 9ff6735d8..99cdb93ea 100644
--- a/go.sum
+++ b/go.sum
@@ -20,10 +20,10 @@ github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
 github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
-go.uber.org/atomic v1.5.0 h1:OI5t8sDa1Or+q8AeE+yKeB/SDYioSHAgcVljj9JIETY=
-go.uber.org/atomic v1.5.0/go.mod h1:sABNBOSYdrvTF6hTgEIbc7YasKWGhgEQZyfxyTvoXHQ=
-go.uber.org/multierr v1.3.0 h1:sFPn2GLc3poCkfrpIXGhBD2X0CMIo4Q/zSULXrj/+uc=
-go.uber.org/multierr v1.3.0/go.mod h1:VgVr7evmIr6uPjLBxg28wmKNXyqE9akIJ5XnfpiKl+4=
+go.uber.org/atomic v1.6.0 h1:Ezj3JGmsOnG1MoRWQkPBsKLe9DwWD9QeXzTRzzldNVk=
+go.uber.org/atomic v1.6.0/go.mod h1:sABNBOSYdrvTF6hTgEIbc7YasKWGhgEQZyfxyTvoXHQ=
+go.uber.org/multierr v1.5.0 h1:KCa4XfM8CWFCpxXRGok+Q0SS/0XBhMDbHHGABQLvD2A=
+go.uber.org/multierr v1.5.0/go.mod h1:FeouvMocqHpRaaGuG9EjoKcStLC43Zu/fmqdUMPcKYU=
 go.uber.org/tools v0.0.0-20190618225709-2cfd321de3ee h1:0mgffUl7nfd+FpvXMVz4IDEaUSmT1ysygQC7qYo7sG4=
 go.uber.org/tools v0.0.0-20190618225709-2cfd321de3ee/go.mod h1:vJERXedbb3MVM5f9Ejo0C68/HhF8uaILCdgjnY+goOA=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
diff --git a/sugar_test.go b/sugar_test.go
index 5b1dcfacd..5f4bb83b9 100644
--- a/sugar_test.go
+++ b/sugar_test.go
@@ -159,10 +159,6 @@ func TestSugarFieldsInvalidPairs(t *testing.T) {
 	})
 }
 
-type stringerF func() string
-
-func (f stringerF) String() string { return f() }
-
 func TestSugarStructuredLogging(t *testing.T) {
 	tests := []struct {
 		msg       string
diff --git a/tools.go b/tools_test.go
similarity index 96%
rename from tools.go
rename to tools_test.go
index 2b6366bea..67e9f5801 100644
--- a/tools.go
+++ b/tools_test.go
@@ -25,4 +25,5 @@ package zap
 import (
 	// Tools we use during development.
 	_ "golang.org/x/lint/golint"
+	_ "honnef.co/go/tools/cmd/staticcheck"
 )
diff --git a/zapcore/encoder_test.go b/zapcore/encoder_test.go
index 3f521971a..54556b8d4 100644
--- a/zapcore/encoder_test.go
+++ b/zapcore/encoder_test.go
@@ -67,14 +67,6 @@ func humanEncoderConfig() EncoderConfig {
 	return cfg
 }
 
-func withJSONEncoder(f func(Encoder)) {
-	f(NewJSONEncoder(testEncoderConfig()))
-}
-
-func withConsoleEncoder(f func(Encoder)) {
-	f(NewConsoleEncoder(humanEncoderConfig()))
-}
-
 func capitalNameEncoder(loggerName string, enc PrimitiveArrayEncoder) {
 	enc.AppendString(strings.ToUpper(loggerName))
 }
diff --git a/zapcore/error.go b/zapcore/error.go
index a67c7bacc..9ba2272c3 100644
--- a/zapcore/error.go
+++ b/zapcore/error.go
@@ -66,11 +66,6 @@ type errorGroup interface {
 	Errors() []error
 }
 
-type causer interface {
-	// Provides access to the error that caused this error.
-	Cause() error
-}
-
 // Note that errArry and errArrayElem are very similar to the version
 // implemented in the top-level error.go file. We can't re-use this because
 // that would require exporting errArray as part of the zapcore API.