diff --git a/src/cmd/go/internal/load/test.go b/src/cmd/go/internal/load/test.go
index 6293aea3c3..48d03d8fce 100644
--- a/src/cmd/go/internal/load/test.go
+++ b/src/cmd/go/internal/load/test.go
@@ -268,17 +268,8 @@ func TestPackagesFor(p *Package, cover *TestCover) (pmain, ptest, pxtest *Packag
 	pmain.Imports = pmain.Imports[:w]
 	pmain.Internal.RawImports = str.StringList(pmain.Imports)
 
-	if ptest != p {
-		// We have made modifications to the package p being tested
-		// and are rebuilding p (as ptest).
-		// Arrange to rebuild all packages q such that
-		// the test depends on q and q depends on p.
-		// This makes sure that q sees the modifications to p.
-		// Strictly speaking, the rebuild is only necessary if the
-		// modifications to p change its export metadata, but
-		// determining that is a bit tricky, so we rebuild always.
-		recompileForTest(pmain, p, ptest, pxtest)
-	}
+	// Replace pmain's transitive dependencies with test copies, as necessary.
+	recompileForTest(pmain, p, ptest, pxtest)
 
 	// Should we apply coverage analysis locally,
 	// only for this package and only for this test?
@@ -325,6 +316,14 @@ Search:
 	return stk
 }
 
+// recompileForTest copies and replaces certain packages in pmain's dependency
+// graph. This is necessary for two reasons. First, if ptest is different than
+// preal, packages that import the package under test should get ptest instead
+// of preal. This is particularly important if pxtest depends on functionality
+// exposed in test sources in ptest. Second, if there is a main package
+// (other than pmain) anywhere, we need to clear p.Internal.BuildInfo in
+// the test copy to prevent link conflicts. This may happen if both -coverpkg
+// and the command line patterns include multiple main packages.
 func recompileForTest(pmain, preal, ptest, pxtest *Package) {
 	// The "test copy" of preal is ptest.
 	// For each package that depends on preal, make a "test copy"
@@ -367,7 +366,7 @@ func recompileForTest(pmain, preal, ptest, pxtest *Package) {
 
 		// Don't compile build info from a main package. This can happen
 		// if -coverpkg patterns include main packages, since those packages
-		// are imported by pmain.
+		// are imported by pmain. See golang.org/issue/30907.
 		if p.Internal.BuildInfo != "" && p != pmain {
 			split()
 		}
diff --git a/src/cmd/go/internal/work/exec.go b/src/cmd/go/internal/work/exec.go
index bbcbdd7568..0ab7976c56 100644
--- a/src/cmd/go/internal/work/exec.go
+++ b/src/cmd/go/internal/work/exec.go
@@ -214,6 +214,7 @@ func (b *Builder) buildActionID(a *Action) cache.ActionID {
 	if p.Internal.CoverMode != "" {
 		fmt.Fprintf(h, "cover %q %q\n", p.Internal.CoverMode, b.toolID("cover"))
 	}
+	fmt.Fprintf(h, "modinfo %q\n", p.Internal.BuildInfo)
 
 	// Configuration specific to compiler toolchain.
 	switch cfg.BuildToolchainName {
diff --git a/src/cmd/go/testdata/script/cover_pkgall_multiple_mains.txt b/src/cmd/go/testdata/script/cover_pkgall_multiple_mains.txt
index 8ee4848d0a..ab7cd66949 100644
--- a/src/cmd/go/testdata/script/cover_pkgall_multiple_mains.txt
+++ b/src/cmd/go/testdata/script/cover_pkgall_multiple_mains.txt
@@ -6,32 +6,38 @@ env GO111MODULE=on
 
 [short] skip
 
-go test -coverpkg=all ./main1 ./main2
+go test -coverpkg=all ./...
 
 -- go.mod --
 module example.com/cov
 
--- main1/main1.go --
+-- mainonly/mainonly.go --
 package main
 
 func main() {}
 
--- main1/main1_test.go --
-package main
-
-import "testing"
-
-func TestMain1(t *testing.T) {}
-
--- main2/main2.go --
+-- mainwithtest/mainwithtest.go --
 package main
 
 func main() {}
 
--- main2/main2_test.go --
+func Foo() {}
+
+-- mainwithtest/mainwithtest_test.go --
 package main
 
 import "testing"
 
-func TestMain2(t *testing.T) {}
+func TestFoo(t *testing.T) {
+  Foo()
+}
 
+-- xtest/x.go --
+package x
+
+-- xtest/x_test.go --
+package x_test
+
+import "testing"
+
+func TestX(t *testing.T) {}